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	$177.43	11.767%	$198.3082	$198.31	$198.30	$198.30
Purchase #2	$71.29	11.725%	$79.6488	$79.65	$79.65	$79.60
Purchase #3	$129.81	10.239%	$143.1012	$143.10	$143.10	$143.10
Purchase #4	$85.48	4.506%	$89.3317	$89.33	$89.35	$89.30
Purchase #5	$173.72	13.601%	$197.3477	$197.35	$197.35	$197.30
Purchase #6	$195.45	12.510%	$219.9008	$219.90	$219.90	$219.90
Purchase #7	$175.77	13.482%	$199.4673	$199.47	$199.45	$199.50
7 purchase totals =	$1,008.95		$1,127.1057	$1,127.11	$1,127.10	$1,127.00