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	$73.67	12.144%	$82.6165	$82.62	$82.60	$82.60
Purchase #2	$50.31	5.554%	$53.1042	$53.10	$53.10	$53.10
Purchase #3	$232.28	10.452%	$256.5579	$256.56	$256.55	$256.60
Purchase #4	$71.54	7.505%	$76.9091	$76.91	$76.90	$76.90
Purchase #5	$149.54	4.850%	$156.7927	$156.79	$156.80	$156.80
Purchase #6	$58.41	7.732%	$62.9263	$62.93	$62.95	$62.90
Purchase #7	$227.86	4.388%	$237.8585	$237.86	$237.85	$237.90
7 purchase totals =	$863.61		$926.7652	$926.77	$926.75	$926.80