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	$235.67	4.514%	$246.3081	$246.31	$246.30	$246.30
Purchase #2	$9.74	5.695%	$10.2947	$10.29	$10.30	$10.30
Purchase #3	$126.46	8.699%	$137.4608	$137.46	$137.45	$137.50
Purchase #4	$85.36	6.123%	$90.5866	$90.59	$90.60	$90.60
Purchase #5	$44.25	13.592%	$50.2645	$50.26	$50.25	$50.30
Purchase #6	$18.95	6.360%	$20.1552	$20.16	$20.15	$20.20
Purchase #7	$183.39	3.352%	$189.5372	$189.54	$189.55	$189.50
7 purchase totals =	$703.82		$744.6071	$744.61	$744.60	$744.70