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	$223.77	4.833%	$234.5848	$234.58	$234.60	$234.60
Purchase #2	$195.83	6.738%	$209.025	$209.03	$209.05	$209.00
Purchase #3	$102.29	13.218%	$115.8107	$115.81	$115.80	$115.80
Purchase #4	$37.96	10.388%	$41.9033	$41.90	$41.90	$41.90
Purchase #5	$137.77	10.822%	$152.6795	$152.68	$152.70	$152.70
Purchase #6	$179.77	12.333%	$201.941	$201.94	$201.95	$201.90
Purchase #7	$104.31	6.805%	$111.4083	$111.41	$111.40	$111.40
7 purchase totals =	$981.70		$1,067.3526	$1,067.35	$1,067.40	$1,067.30