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	$148.35	11.393%	$165.2515	$165.25	$165.25	$165.30
Purchase #2	$113.70	4.345%	$118.6403	$118.64	$118.65	$118.60
Purchase #3	$211.46	10.254%	$233.1431	$233.14	$233.15	$233.10
Purchase #4	$248.29	4.812%	$260.2377	$260.24	$260.25	$260.20
Purchase #5	$125.90	12.755%	$141.9585	$141.96	$141.95	$142.00
Purchase #6	$223.85	4.749%	$234.4806	$234.48	$234.50	$234.50
Purchase #7	$54.63	13.106%	$61.7898	$61.79	$61.80	$61.80
7 purchase totals =	$1,126.18		$1,215.5015	$1,215.50	$1,215.55	$1,215.50