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	$11.48	4.174%	$11.9592	$11.96	$11.95	$12.00
Purchase #2	$24.48	5.797%	$25.8991	$25.90	$25.90	$25.90
Purchase #3	$215.64	3.279%	$222.7108	$222.71	$222.70	$222.70
Purchase #4	$226.54	12.344%	$254.5041	$254.50	$254.50	$254.50
Purchase #5	$147.56	9.190%	$161.1208	$161.12	$161.10	$161.10
Purchase #6	$47.90	11.741%	$53.5239	$53.52	$53.50	$53.50
Purchase #7	$42.70	6.594%	$45.5156	$45.52	$45.50	$45.50
7 purchase totals =	$716.30		$775.2335	$775.23	$775.15	$775.20