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	$118.91	11.203%	$132.2315	$132.23	$132.25	$132.20
Purchase #2	$240.25	11.303%	$267.4055	$267.41	$267.40	$267.40
Purchase #3	$171.90	8.128%	$185.872	$185.87	$185.85	$185.90
Purchase #4	$62.60	13.789%	$71.2319	$71.23	$71.25	$71.20
Purchase #5	$231.62	9.476%	$253.5683	$253.57	$253.55	$253.60
Purchase #6	$17.65	8.691%	$19.184	$19.18	$19.20	$19.20
Purchase #7	$29.89	7.367%	$32.092	$32.09	$32.10	$32.10
7 purchase totals =	$872.82		$961.5852	$961.58	$961.60	$961.60