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	$32.34	4.864%	$33.913	$33.91	$33.90	$33.90
Purchase #2	$76.32	11.663%	$85.2212	$85.22	$85.20	$85.20
Purchase #3	$106.46	12.263%	$119.5152	$119.52	$119.50	$119.50
Purchase #4	$183.78	9.339%	$200.9432	$200.94	$200.95	$200.90
Purchase #5	$63.63	12.865%	$71.816	$71.82	$71.80	$71.80
Purchase #6	$216.82	6.383%	$230.6596	$230.66	$230.65	$230.70
Purchase #7	$66.63	3.765%	$69.1386	$69.14	$69.15	$69.10
7 purchase totals =	$745.98		$811.2068	$811.21	$811.15	$811.10