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	$177.94	12.119%	$199.5045	$199.50	$199.50	$199.50
Purchase #2	$148.46	6.689%	$158.3905	$158.39	$158.40	$158.40
Purchase #3	$119.82	7.554%	$128.8712	$128.87	$128.85	$128.90
Purchase #4	$138.49	11.226%	$154.0369	$154.04	$154.05	$154.00
Purchase #5	$18.89	6.131%	$20.0481	$20.05	$20.05	$20.00
Purchase #6	$181.79	11.708%	$203.074	$203.07	$203.05	$203.10
Purchase #7	$218.44	13.236%	$247.3527	$247.35	$247.35	$247.40
7 purchase totals =	$1,003.83		$1,111.2779	$1,111.27	$1,111.25	$1,111.30