Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.33	13.759%	$190.3529	$190.35	$190.35	$190.40
Purchase #2	$176.32	13.306%	$199.7811	$199.78	$199.80	$199.80
Purchase #3	$155.25	8.341%	$168.1994	$168.20	$168.20	$168.20
Purchase #4	$105.61	3.681%	$109.4975	$109.50	$109.50	$109.50
Purchase #5	$150.43	12.464%	$169.1796	$169.18	$169.20	$169.20
Purchase #6	$224.27	7.179%	$240.3703	$240.37	$240.35	$240.40
Purchase #7	$240.82	10.756%	$266.7226	$266.72	$266.70	$266.70
7 purchase totals =	$1,220.03		$1,344.1034	$1,344.10	$1,344.10	$1,344.20