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	$186.66	4.281%	$194.6509	$194.65	$194.65	$194.70
Purchase #2	$136.39	11.365%	$151.8907	$151.89	$151.90	$151.90
Purchase #3	$230.79	9.634%	$253.0243	$253.02	$253.00	$253.00
Purchase #4	$107.36	10.755%	$118.9066	$118.91	$118.90	$118.90
Purchase #5	$240.85	13.690%	$273.8224	$273.82	$273.80	$273.80
Purchase #6	$234.25	13.513%	$265.9042	$265.90	$265.90	$265.90
Purchase #7	$224.54	7.613%	$241.6342	$241.63	$241.65	$241.60
7 purchase totals =	$1,360.84		$1,499.8333	$1,499.82	$1,499.80	$1,499.80