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	$144.90	7.219%	$155.3603	$155.36	$155.35	$155.40
Purchase #2	$177.60	10.138%	$195.6051	$195.61	$195.60	$195.60
Purchase #3	$140.50	7.748%	$151.3859	$151.39	$151.40	$151.40
Purchase #4	$190.43	6.843%	$203.4611	$203.46	$203.45	$203.50
Purchase #5	$45.66	7.215%	$48.9544	$48.95	$48.95	$49.00
Purchase #6	$166.63	7.360%	$178.894	$178.89	$178.90	$178.90
Purchase #7	$59.35	5.404%	$62.5573	$62.56	$62.55	$62.60
7 purchase totals =	$925.07		$996.2181	$996.22	$996.20	$996.40