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	$76.59	11.331%	$85.2684	$85.27	$85.25	$85.30
Purchase #2	$197.49	9.871%	$216.9842	$216.98	$217.00	$217.00
Purchase #3	$121.52	4.650%	$127.1707	$127.17	$127.15	$127.20
Purchase #4	$84.49	12.597%	$95.1332	$95.13	$95.15	$95.10
Purchase #5	$109.80	13.760%	$124.9085	$124.91	$124.90	$124.90
Purchase #6	$153.47	7.665%	$165.2335	$165.23	$165.25	$165.20
Purchase #7	$219.50	8.589%	$238.3529	$238.35	$238.35	$238.40
7 purchase totals =	$962.86		$1,053.0514	$1,053.04	$1,053.05	$1,053.10