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	$236.43	5.761%	$250.0507	$250.05	$250.05	$250.10
Purchase #2	$87.35	13.534%	$99.1719	$99.17	$99.15	$99.20
Purchase #3	$249.62	7.200%	$267.5926	$267.59	$267.60	$267.60
Purchase #4	$237.91	13.362%	$269.6995	$269.70	$269.70	$269.70
Purchase #5	$46.59	12.650%	$52.4836	$52.48	$52.50	$52.50
Purchase #6	$92.64	11.620%	$103.4048	$103.40	$103.40	$103.40
Purchase #7	$54.26	13.221%	$61.4337	$61.43	$61.45	$61.40
7 purchase totals =	$1,004.80		$1,103.8368	$1,103.82	$1,103.85	$1,103.90