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	$81.40	13.734%	$92.5795	$92.58	$92.60	$92.60
Purchase #2	$39.64	5.405%	$41.7825	$41.78	$41.80	$41.80
Purchase #3	$144.41	5.846%	$152.8522	$152.85	$152.85	$152.90
Purchase #4	$45.78	5.805%	$48.4375	$48.44	$48.45	$48.40
Purchase #5	$195.46	13.231%	$221.3213	$221.32	$221.30	$221.30
Purchase #6	$107.31	13.356%	$121.6423	$121.64	$121.65	$121.60
Purchase #7	$185.59	6.146%	$196.9964	$197.00	$197.00	$197.00
7 purchase totals =	$799.59		$875.6117	$875.61	$875.65	$875.60