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	$73.59	11.816%	$82.2854	$82.29	$82.30	$82.30
Purchase #2	$20.60	6.550%	$21.9493	$21.95	$21.95	$21.90
Purchase #3	$19.84	13.462%	$22.5109	$22.51	$22.50	$22.50
Purchase #4	$182.26	10.132%	$200.7266	$200.73	$200.75	$200.70
Purchase #5	$56.82	4.479%	$59.365	$59.37	$59.35	$59.40
Purchase #6	$18.91	11.617%	$21.1068	$21.11	$21.10	$21.10
Purchase #7	$29.63	10.401%	$32.7118	$32.71	$32.70	$32.70
7 purchase totals =	$401.65		$440.6558	$440.67	$440.65	$440.60