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	$141.56	7.403%	$152.0397	$152.04	$152.05	$152.00
Purchase #2	$63.55	12.652%	$71.5903	$71.59	$71.60	$71.60
Purchase #3	$150.31	9.815%	$165.0629	$165.06	$165.05	$165.10
Purchase #4	$243.94	11.414%	$271.7833	$271.78	$271.80	$271.80
Purchase #5	$112.57	7.227%	$120.7054	$120.71	$120.70	$120.70
Purchase #6	$38.26	6.381%	$40.7014	$40.70	$40.70	$40.70
Purchase #7	$180.90	4.346%	$188.7619	$188.76	$188.75	$188.80
7 purchase totals =	$931.09		$1,010.6449	$1,010.64	$1,010.65	$1,010.70