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	$196.69	11.761%	$219.8227	$219.82	$219.80	$219.80
Purchase #2	$83.37	12.188%	$93.5311	$93.53	$93.55	$93.50
Purchase #3	$126.47	4.793%	$132.5317	$132.53	$132.55	$132.50
Purchase #4	$161.51	7.657%	$173.8768	$173.88	$173.90	$173.90
Purchase #5	$199.67	6.253%	$212.1554	$212.16	$212.15	$212.20
Purchase #6	$189.98	3.626%	$196.8687	$196.87	$196.85	$196.90
Purchase #7	$228.32	13.331%	$258.7573	$258.76	$258.75	$258.80
7 purchase totals =	$1,186.01		$1,287.5437	$1,287.55	$1,287.55	$1,287.60