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	$174.36	5.464%	$183.887	$183.89	$183.90	$183.90
Purchase #2	$155.51	10.320%	$171.5586	$171.56	$171.55	$171.60
Purchase #3	$17.27	8.332%	$18.7089	$18.71	$18.70	$18.70
Purchase #4	$38.48	5.629%	$40.646	$40.65	$40.65	$40.60
Purchase #5	$163.73	7.790%	$176.4846	$176.48	$176.50	$176.50
Purchase #6	$211.85	3.116%	$218.4512	$218.45	$218.45	$218.50
Purchase #7	$42.64	6.635%	$45.4692	$45.47	$45.45	$45.50
7 purchase totals =	$803.84		$855.2055	$855.21	$855.20	$855.30