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	$169.32	12.296%	$190.1396	$190.14	$190.15	$190.10
Purchase #2	$52.73	3.374%	$54.5091	$54.51	$54.50	$54.50
Purchase #3	$211.35	7.512%	$227.2266	$227.23	$227.25	$227.20
Purchase #4	$34.61	6.767%	$36.9521	$36.95	$36.95	$37.00
Purchase #5	$62.97	5.289%	$66.3005	$66.30	$66.30	$66.30
Purchase #6	$42.35	3.446%	$43.8094	$43.81	$43.80	$43.80
Purchase #7	$63.96	11.756%	$71.4791	$71.48	$71.50	$71.50
7 purchase totals =	$637.29		$690.4164	$690.42	$690.45	$690.40