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	$247.86	6.208%	$263.2471	$263.25	$263.25	$263.20
Purchase #2	$203.82	9.166%	$222.5021	$222.50	$222.50	$222.50
Purchase #3	$126.79	11.532%	$141.4114	$141.41	$141.40	$141.40
Purchase #4	$50.84	11.163%	$56.5153	$56.52	$56.50	$56.50
Purchase #5	$124.46	5.588%	$131.4148	$131.41	$131.40	$131.40
Purchase #6	$16.35	4.408%	$17.0707	$17.07	$17.05	$17.10
Purchase #7	$202.38	13.235%	$229.165	$229.17	$229.15	$229.20
7 purchase totals =	$972.50		$1,061.3264	$1,061.33	$1,061.25	$1,061.30