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	$154.65	12.571%	$174.0911	$174.09	$174.10	$174.10
Purchase #2	$150.31	8.368%	$162.8879	$162.89	$162.90	$162.90
Purchase #3	$132.95	11.741%	$148.5597	$148.56	$148.55	$148.60
Purchase #4	$171.61	5.176%	$180.4925	$180.49	$180.50	$180.50
Purchase #5	$242.55	13.598%	$275.5319	$275.53	$275.55	$275.50
Purchase #6	$146.45	6.270%	$155.6324	$155.63	$155.65	$155.60
Purchase #7	$74.82	5.175%	$78.6919	$78.69	$78.70	$78.70
7 purchase totals =	$1,073.34		$1,175.8874	$1,175.88	$1,175.95	$1,175.90