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	$144.72	4.799%	$151.6651	$151.67	$151.65	$151.70
Purchase #2	$121.41	4.843%	$127.2899	$127.29	$127.30	$127.30
Purchase #3	$250.29	10.312%	$276.0999	$276.10	$276.10	$276.10
Purchase #4	$41.37	11.386%	$46.0804	$46.08	$46.10	$46.10
Purchase #5	$67.73	6.451%	$72.0993	$72.10	$72.10	$72.10
Purchase #6	$218.97	8.585%	$237.7686	$237.77	$237.75	$237.80
Purchase #7	$30.51	6.653%	$32.5398	$32.54	$32.55	$32.50
7 purchase totals =	$875.00		$943.5430	$943.55	$943.55	$943.60