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	$195.64	12.191%	$219.4905	$219.49	$219.50	$219.50
Purchase #2	$76.68	7.629%	$82.5299	$82.53	$82.55	$82.50
Purchase #3	$243.95	8.391%	$264.4198	$264.42	$264.40	$264.40
Purchase #4	$37.74	3.548%	$39.079	$39.08	$39.10	$39.10
Purchase #5	$95.81	4.227%	$99.8599	$99.86	$99.85	$99.90
Purchase #6	$87.48	3.762%	$90.771	$90.77	$90.75	$90.80
Purchase #7	$197.48	8.478%	$214.2224	$214.22	$214.20	$214.20
7 purchase totals =	$934.78		$1,010.3725	$1,010.37	$1,010.35	$1,010.40