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	$59.39	3.197%	$61.2887	$61.29	$61.30	$61.30
Purchase #2	$163.93	7.374%	$176.0182	$176.02	$176.00	$176.00
Purchase #3	$114.55	7.847%	$123.5387	$123.54	$123.55	$123.50
Purchase #4	$156.54	6.560%	$166.809	$166.81	$166.80	$166.80
Purchase #5	$191.76	12.711%	$216.1346	$216.13	$216.15	$216.10
Purchase #6	$14.83	13.766%	$16.8715	$16.87	$16.85	$16.90
Purchase #7	$151.30	13.843%	$172.2445	$172.24	$172.25	$172.20
7 purchase totals =	$852.30		$932.9052	$932.90	$932.90	$932.80