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	$55.98	11.308%	$62.3102	$62.31	$62.30	$62.30
Purchase #2	$51.65	11.437%	$57.5572	$57.56	$57.55	$57.60
Purchase #3	$92.43	8.577%	$100.3577	$100.36	$100.35	$100.40
Purchase #4	$167.29	13.485%	$189.8491	$189.85	$189.85	$189.80
Purchase #5	$160.70	11.345%	$178.9314	$178.93	$178.95	$178.90
Purchase #6	$60.54	3.659%	$62.7552	$62.76	$62.75	$62.80
Purchase #7	$193.60	11.771%	$216.3887	$216.39	$216.40	$216.40
7 purchase totals =	$782.19		$868.1495	$868.16	$868.15	$868.20