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	$232.72	10.374%	$256.8624	$256.86	$256.85	$256.90
Purchase #2	$91.54	12.837%	$103.291	$103.29	$103.30	$103.30
Purchase #3	$175.27	13.624%	$199.1488	$199.15	$199.15	$199.10
Purchase #4	$109.58	8.165%	$118.5272	$118.53	$118.55	$118.50
Purchase #5	$221.86	12.608%	$249.8321	$249.83	$249.85	$249.80
Purchase #6	$111.92	6.450%	$119.1388	$119.14	$119.15	$119.10
Purchase #7	$195.41	13.515%	$221.8197	$221.82	$221.80	$221.80
7 purchase totals =	$1,138.30		$1,268.6200	$1,268.62	$1,268.65	$1,268.50