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	$118.51	13.802%	$134.8668	$134.87	$134.85	$134.90
Purchase #2	$62.89	4.147%	$65.498	$65.50	$65.50	$65.50
Purchase #3	$153.61	4.666%	$160.7774	$160.78	$160.80	$160.80
Purchase #4	$214.60	12.119%	$240.6074	$240.61	$240.60	$240.60
Purchase #5	$121.54	11.797%	$135.8781	$135.88	$135.90	$135.90
Purchase #6	$150.56	10.153%	$165.8464	$165.85	$165.85	$165.80
Purchase #7	$124.72	13.495%	$141.551	$141.55	$141.55	$141.60
7 purchase totals =	$946.43		$1,045.0251	$1,045.04	$1,045.05	$1,045.10