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	$216.75	9.105%	$236.4851	$236.49	$236.50	$236.50
Purchase #2	$8.47	3.546%	$8.7703	$8.77	$8.75	$8.80
Purchase #3	$82.44	3.731%	$85.5158	$85.52	$85.50	$85.50
Purchase #4	$39.39	4.858%	$41.3036	$41.30	$41.30	$41.30
Purchase #5	$156.52	5.783%	$165.5716	$165.57	$165.55	$165.60
Purchase #6	$198.76	12.469%	$223.5434	$223.54	$223.55	$223.50
Purchase #7	$52.52	4.620%	$54.9464	$54.95	$54.95	$54.90
7 purchase totals =	$754.85		$816.1362	$816.14	$816.10	$816.10