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	$63.53	13.148%	$71.8829	$71.88	$71.90	$71.90
Purchase #2	$140.34	7.163%	$150.3926	$150.39	$150.40	$150.40
Purchase #3	$105.90	4.485%	$110.6496	$110.65	$110.65	$110.60
Purchase #4	$159.63	6.405%	$169.8543	$169.85	$169.85	$169.90
Purchase #5	$99.57	9.258%	$108.7882	$108.79	$108.80	$108.80
Purchase #6	$214.96	5.623%	$227.0472	$227.05	$227.05	$227.00
Purchase #7	$40.67	4.255%	$42.4005	$42.40	$42.40	$42.40
7 purchase totals =	$824.60		$881.0153	$881.01	$881.05	$881.00