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	$239.70	10.106%	$263.9241	$263.92	$263.90	$263.90
Purchase #2	$130.46	7.498%	$140.2419	$140.24	$140.25	$140.20
Purchase #3	$44.39	13.132%	$50.2193	$50.22	$50.20	$50.20
Purchase #4	$195.45	13.131%	$221.1145	$221.11	$221.10	$221.10
Purchase #5	$136.27	12.190%	$152.8813	$152.88	$152.90	$152.90
Purchase #6	$174.78	5.761%	$184.8491	$184.85	$184.85	$184.80
Purchase #7	$122.65	12.121%	$137.5164	$137.52	$137.50	$137.50
7 purchase totals =	$1,043.70		$1,150.7466	$1,150.74	$1,150.70	$1,150.60