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	$136.66	10.558%	$151.0886	$151.09	$151.10	$151.10
Purchase #2	$96.48	3.171%	$99.5394	$99.54	$99.55	$99.50
Purchase #3	$186.36	13.332%	$211.2055	$211.21	$211.20	$211.20
Purchase #4	$136.93	9.472%	$149.9	$149.90	$149.90	$149.90
Purchase #5	$154.37	3.757%	$160.1697	$160.17	$160.15	$160.20
Purchase #6	$99.39	4.593%	$103.955	$103.96	$103.95	$104.00
Purchase #7	$66.45	9.128%	$72.5156	$72.52	$72.50	$72.50
7 purchase totals =	$876.64		$948.3738	$948.39	$948.35	$948.40