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	$183.55	3.652%	$190.2532	$190.25	$190.25	$190.30
Purchase #2	$163.43	13.369%	$185.279	$185.28	$185.30	$185.30
Purchase #3	$213.61	5.288%	$224.9057	$224.91	$224.90	$224.90
Purchase #4	$94.62	11.822%	$105.806	$105.81	$105.80	$105.80
Purchase #5	$248.52	7.210%	$266.4383	$266.44	$266.45	$266.40
Purchase #6	$52.32	8.408%	$56.7191	$56.72	$56.70	$56.70
Purchase #7	$25.89	7.202%	$27.7546	$27.75	$27.75	$27.80
7 purchase totals =	$981.94		$1,057.1559	$1,057.16	$1,057.15	$1,057.20