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	$89.54	10.228%	$98.6982	$98.70	$98.70	$98.70
Purchase #2	$81.29	11.723%	$90.8196	$90.82	$90.80	$90.80
Purchase #3	$190.35	3.299%	$196.6296	$196.63	$196.65	$196.60
Purchase #4	$106.53	4.604%	$111.4346	$111.43	$111.45	$111.40
Purchase #5	$94.67	11.110%	$105.1878	$105.19	$105.20	$105.20
Purchase #6	$139.38	11.360%	$155.2136	$155.21	$155.20	$155.20
Purchase #7	$194.89	5.168%	$204.9619	$204.96	$204.95	$205.00
7 purchase totals =	$896.65		$962.9453	$962.94	$962.95	$962.90