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	$91.89	10.362%	$101.4116	$101.41	$101.40	$101.40
Purchase #2	$92.72	8.561%	$100.6578	$100.66	$100.65	$100.70
Purchase #3	$153.37	10.789%	$169.9171	$169.92	$169.90	$169.90
Purchase #4	$37.38	8.263%	$40.4687	$40.47	$40.45	$40.50
Purchase #5	$200.38	4.604%	$209.6055	$209.61	$209.60	$209.60
Purchase #6	$58.42	13.535%	$66.3271	$66.33	$66.35	$66.30
Purchase #7	$188.39	10.736%	$208.6156	$208.62	$208.60	$208.60
7 purchase totals =	$822.55		$897.0034	$897.02	$896.95	$897.00