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	$241.73	11.306%	$269.06	$269.06	$269.05	$269.10
Purchase #2	$128.35	10.562%	$141.9063	$141.91	$141.90	$141.90
Purchase #3	$57.25	4.176%	$59.6408	$59.64	$59.65	$59.60
Purchase #4	$169.41	13.201%	$191.7738	$191.77	$191.75	$191.80
Purchase #5	$45.53	11.373%	$50.7081	$50.71	$50.70	$50.70
Purchase #6	$53.52	12.809%	$60.3754	$60.38	$60.40	$60.40
Purchase #7	$156.91	5.733%	$165.9057	$165.91	$165.90	$165.90
7 purchase totals =	$852.70		$939.3701	$939.38	$939.35	$939.40