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	$73.48	12.497%	$82.6628	$82.66	$82.65	$82.70
Purchase #2	$183.78	13.370%	$208.3514	$208.35	$208.35	$208.40
Purchase #3	$40.42	11.732%	$45.1621	$45.16	$45.15	$45.20
Purchase #4	$188.35	4.283%	$196.417	$196.42	$196.40	$196.40
Purchase #5	$57.96	6.718%	$61.8538	$61.85	$61.85	$61.90
Purchase #6	$228.46	8.634%	$248.1852	$248.19	$248.20	$248.20
Purchase #7	$235.83	11.258%	$262.3797	$262.38	$262.40	$262.40
7 purchase totals =	$1,008.28		$1,105.0120	$1,105.01	$1,105.00	$1,105.20