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	$149.48	6.290%	$158.8823	$158.88	$158.90	$158.90
Purchase #2	$159.69	3.432%	$165.1706	$165.17	$165.15	$165.20
Purchase #3	$13.38	8.317%	$14.4928	$14.49	$14.50	$14.50
Purchase #4	$176.36	11.208%	$196.1264	$196.13	$196.15	$196.10
Purchase #5	$159.64	11.541%	$178.0641	$178.06	$178.05	$178.10
Purchase #6	$223.32	10.302%	$246.3264	$246.33	$246.35	$246.30
Purchase #7	$50.44	9.532%	$55.2479	$55.25	$55.25	$55.20
7 purchase totals =	$932.31		$1,014.3105	$1,014.31	$1,014.35	$1,014.30