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	$76.89	11.519%	$85.747	$85.75	$85.75	$85.70
Purchase #2	$250.36	11.233%	$278.4829	$278.48	$278.50	$278.50
Purchase #3	$167.57	12.667%	$188.7961	$188.80	$188.80	$188.80
Purchase #4	$250.43	9.141%	$273.3218	$273.32	$273.30	$273.30
Purchase #5	$42.28	5.805%	$44.7344	$44.73	$44.75	$44.70
Purchase #6	$139.85	8.316%	$151.4799	$151.48	$151.50	$151.50
Purchase #7	$182.37	4.310%	$190.2301	$190.23	$190.25	$190.20
7 purchase totals =	$1,109.75		$1,212.7922	$1,212.79	$1,212.85	$1,212.70