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	$154.89	13.756%	$176.1967	$176.20	$176.20	$176.20
Purchase #2	$136.90	9.864%	$150.4038	$150.40	$150.40	$150.40
Purchase #3	$98.28	7.829%	$105.9743	$105.97	$105.95	$106.00
Purchase #4	$78.96	13.664%	$89.7491	$89.75	$89.75	$89.70
Purchase #5	$71.76	9.166%	$78.3375	$78.34	$78.35	$78.30
Purchase #6	$250.61	10.258%	$276.3176	$276.32	$276.30	$276.30
Purchase #7	$40.72	13.139%	$46.0702	$46.07	$46.05	$46.10
7 purchase totals =	$832.12		$923.0492	$923.05	$923.00	$923.00