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	$116.40	5.787%	$123.1361	$123.14	$123.15	$123.10
Purchase #2	$171.82	6.148%	$182.3835	$182.38	$182.40	$182.40
Purchase #3	$40.58	13.496%	$46.0567	$46.06	$46.05	$46.10
Purchase #4	$194.65	9.374%	$212.8965	$212.90	$212.90	$212.90
Purchase #5	$48.48	4.269%	$50.5496	$50.55	$50.55	$50.50
Purchase #6	$63.29	13.379%	$71.7576	$71.76	$71.75	$71.80
Purchase #7	$149.76	10.447%	$165.4054	$165.41	$165.40	$165.40
7 purchase totals =	$784.98		$852.1854	$852.20	$852.20	$852.20