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	$220.82	7.502%	$237.3859	$237.39	$237.40	$237.40
Purchase #2	$178.66	3.785%	$185.4223	$185.42	$185.40	$185.40
Purchase #3	$118.36	10.172%	$130.3996	$130.40	$130.40	$130.40
Purchase #4	$86.66	4.343%	$90.4236	$90.42	$90.40	$90.40
Purchase #5	$242.89	3.170%	$250.5896	$250.59	$250.60	$250.60
Purchase #6	$70.89	6.562%	$75.5418	$75.54	$75.55	$75.50
Purchase #7	$72.91	4.117%	$75.9117	$75.91	$75.90	$75.90
7 purchase totals =	$991.19		$1,045.6745	$1,045.67	$1,045.65	$1,045.60