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	$201.81	4.501%	$210.8935	$210.89	$210.90	$210.90
Purchase #2	$229.47	6.722%	$244.895	$244.90	$244.90	$244.90
Purchase #3	$40.94	13.789%	$46.5852	$46.59	$46.60	$46.60
Purchase #4	$52.97	11.799%	$59.2199	$59.22	$59.20	$59.20
Purchase #5	$15.37	3.717%	$15.9413	$15.94	$15.95	$15.90
Purchase #6	$238.65	3.522%	$247.0553	$247.06	$247.05	$247.10
Purchase #7	$69.52	13.341%	$78.7947	$78.79	$78.80	$78.80
7 purchase totals =	$848.73		$903.3849	$903.39	$903.40	$903.40