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	$250.86	8.682%	$272.6397	$272.64	$272.65	$272.60
Purchase #2	$124.73	8.712%	$135.5965	$135.60	$135.60	$135.60
Purchase #3	$105.75	5.362%	$111.4203	$111.42	$111.40	$111.40
Purchase #4	$96.28	4.594%	$100.7031	$100.70	$100.70	$100.70
Purchase #5	$90.55	8.514%	$98.2594	$98.26	$98.25	$98.30
Purchase #6	$57.53	7.581%	$61.8913	$61.89	$61.90	$61.90
Purchase #7	$112.60	10.485%	$124.4061	$124.41	$124.40	$124.40
7 purchase totals =	$838.30		$904.9164	$904.92	$904.90	$904.90