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	$222.71	6.813%	$237.8832	$237.88	$237.90	$237.90
Purchase #2	$247.35	6.217%	$262.7277	$262.73	$262.75	$262.70
Purchase #3	$84.32	6.443%	$89.7527	$89.75	$89.75	$89.80
Purchase #4	$133.56	10.852%	$148.0539	$148.05	$148.05	$148.10
Purchase #5	$17.52	9.428%	$19.1718	$19.17	$19.15	$19.20
Purchase #6	$161.49	3.345%	$166.8918	$166.89	$166.90	$166.90
Purchase #7	$223.83	4.790%	$234.5515	$234.55	$234.55	$234.60
7 purchase totals =	$1,090.78		$1,159.0326	$1,159.02	$1,159.05	$1,159.20