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	$56.54	13.778%	$64.3301	$64.33	$64.35	$64.30
Purchase #2	$246.86	11.589%	$275.4686	$275.47	$275.45	$275.50
Purchase #3	$38.50	8.307%	$41.6982	$41.70	$41.70	$41.70
Purchase #4	$192.41	11.190%	$213.9407	$213.94	$213.95	$213.90
Purchase #5	$152.52	6.649%	$162.6611	$162.66	$162.65	$162.70
Purchase #6	$55.76	6.366%	$59.3097	$59.31	$59.30	$59.30
Purchase #7	$208.83	13.810%	$237.6694	$237.67	$237.65	$237.70
7 purchase totals =	$951.42		$1,055.0778	$1,055.08	$1,055.05	$1,055.10