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	$148.90	5.122%	$156.5267	$156.53	$156.55	$156.50
Purchase #2	$169.65	12.530%	$190.9071	$190.91	$190.90	$190.90
Purchase #3	$105.97	12.738%	$119.4685	$119.47	$119.45	$119.50
Purchase #4	$41.66	9.400%	$45.576	$45.58	$45.60	$45.60
Purchase #5	$125.45	13.684%	$142.6166	$142.62	$142.60	$142.60
Purchase #6	$177.74	9.579%	$194.7657	$194.77	$194.75	$194.80
Purchase #7	$144.96	6.589%	$154.5114	$154.51	$154.50	$154.50
7 purchase totals =	$914.33		$1,004.3720	$1,004.39	$1,004.35	$1,004.40