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	$132.76	12.551%	$149.4227	$149.42	$149.40	$149.40
Purchase #2	$112.29	10.719%	$124.3264	$124.33	$124.35	$124.30
Purchase #3	$156.51	7.404%	$168.098	$168.10	$168.10	$168.10
Purchase #4	$211.77	12.829%	$238.938	$238.94	$238.95	$238.90
Purchase #5	$54.59	4.322%	$56.9494	$56.95	$56.95	$56.90
Purchase #6	$131.99	5.325%	$139.0185	$139.02	$139.00	$139.00
Purchase #7	$69.46	3.572%	$71.9411	$71.94	$71.95	$71.90
7 purchase totals =	$869.37		$948.6941	$948.70	$948.70	$948.50