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	$212.67	11.863%	$237.899	$237.90	$237.90	$237.90
Purchase #2	$88.92	11.817%	$99.4277	$99.43	$99.45	$99.40
Purchase #3	$196.58	10.308%	$216.8435	$216.84	$216.85	$216.80
Purchase #4	$147.98	9.784%	$162.4584	$162.46	$162.45	$162.50
Purchase #5	$242.83	8.492%	$263.4511	$263.45	$263.45	$263.50
Purchase #6	$148.56	7.637%	$159.9055	$159.91	$159.90	$159.90
Purchase #7	$175.86	13.352%	$199.3408	$199.34	$199.35	$199.30
7 purchase totals =	$1,213.40		$1,339.3260	$1,339.33	$1,339.35	$1,339.30