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	$23.45	7.519%	$25.2132	$25.21	$25.20	$25.20
Purchase #2	$200.45	5.617%	$211.7093	$211.71	$211.70	$211.70
Purchase #3	$75.76	13.534%	$86.0134	$86.01	$86.00	$86.00
Purchase #4	$20.92	7.324%	$22.4522	$22.45	$22.45	$22.50
Purchase #5	$99.36	6.144%	$105.4647	$105.46	$105.45	$105.50
Purchase #6	$37.77	7.136%	$40.4653	$40.47	$40.45	$40.50
Purchase #7	$106.81	3.221%	$110.2504	$110.25	$110.25	$110.30
7 purchase totals =	$564.52		$601.5685	$601.56	$601.50	$601.70