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	$223.81	11.801%	$250.2218	$250.22	$250.20	$250.20
Purchase #2	$43.98	9.741%	$48.2641	$48.26	$48.25	$48.30
Purchase #3	$215.85	8.319%	$233.8066	$233.81	$233.80	$233.80
Purchase #4	$237.45	11.701%	$265.234	$265.23	$265.25	$265.20
Purchase #5	$196.86	6.373%	$209.4059	$209.41	$209.40	$209.40
Purchase #6	$97.67	7.594%	$105.0871	$105.09	$105.10	$105.10
Purchase #7	$99.86	13.662%	$113.5029	$113.50	$113.50	$113.50
7 purchase totals =	$1,115.48		$1,225.5224	$1,225.52	$1,225.50	$1,225.50