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	$21.91	3.612%	$22.7014	$22.70	$22.70	$22.70
Purchase #2	$246.40	7.748%	$265.4911	$265.49	$265.50	$265.50
Purchase #3	$154.54	7.213%	$165.687	$165.69	$165.70	$165.70
Purchase #4	$112.85	4.837%	$118.3086	$118.31	$118.30	$118.30
Purchase #5	$82.96	8.588%	$90.0846	$90.08	$90.10	$90.10
Purchase #6	$215.32	10.848%	$238.6779	$238.68	$238.70	$238.70
Purchase #7	$125.51	9.534%	$137.4761	$137.48	$137.50	$137.50
7 purchase totals =	$959.49		$1,038.4267	$1,038.43	$1,038.50	$1,038.50