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	$160.25	9.699%	$175.7926	$175.79	$175.80	$175.80
Purchase #2	$116.75	12.705%	$131.5831	$131.58	$131.60	$131.60
Purchase #3	$48.93	13.871%	$55.7171	$55.72	$55.70	$55.70
Purchase #4	$247.32	6.764%	$264.0487	$264.05	$264.05	$264.00
Purchase #5	$195.83	10.392%	$216.1807	$216.18	$216.20	$216.20
Purchase #6	$12.75	10.612%	$14.103	$14.10	$14.10	$14.10
Purchase #7	$139.34	9.335%	$152.3474	$152.35	$152.35	$152.30
7 purchase totals =	$921.17		$1,009.7726	$1,009.77	$1,009.80	$1,009.70