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	$188.46	9.126%	$205.6589	$205.66	$205.65	$205.70
Purchase #2	$188.26	9.637%	$206.4026	$206.40	$206.40	$206.40
Purchase #3	$93.68	6.368%	$99.6455	$99.65	$99.65	$99.60
Purchase #4	$27.88	13.815%	$31.7316	$31.73	$31.75	$31.70
Purchase #5	$35.91	5.429%	$37.8596	$37.86	$37.85	$37.90
Purchase #6	$147.31	3.123%	$151.9105	$151.91	$151.90	$151.90
Purchase #7	$203.82	13.445%	$231.2236	$231.22	$231.20	$231.20
7 purchase totals =	$885.32		$964.4323	$964.43	$964.40	$964.40