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	$36.58	13.533%	$41.5304	$41.53	$41.55	$41.50
Purchase #2	$46.86	6.360%	$49.8403	$49.84	$49.85	$49.80
Purchase #3	$88.35	12.733%	$99.5996	$99.60	$99.60	$99.60
Purchase #4	$47.50	4.282%	$49.534	$49.53	$49.55	$49.50
Purchase #5	$41.93	8.241%	$45.3855	$45.39	$45.40	$45.40
Purchase #6	$58.44	10.139%	$64.3652	$64.37	$64.35	$64.40
Purchase #7	$175.52	12.130%	$196.8106	$196.81	$196.80	$196.80
7 purchase totals =	$495.18		$547.0656	$547.07	$547.10	$547.00