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	$222.89	4.139%	$232.1154	$232.12	$232.10	$232.10
Purchase #2	$132.47	12.433%	$148.94	$148.94	$148.95	$148.90
Purchase #3	$141.33	8.285%	$153.0392	$153.04	$153.05	$153.00
Purchase #4	$90.26	10.283%	$99.5414	$99.54	$99.55	$99.50
Purchase #5	$151.94	10.474%	$167.8542	$167.85	$167.85	$167.90
Purchase #6	$25.85	8.244%	$27.9811	$27.98	$28.00	$28.00
Purchase #7	$165.72	13.529%	$188.1403	$188.14	$188.15	$188.10
7 purchase totals =	$930.46		$1,017.6116	$1,017.61	$1,017.65	$1,017.50