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	$44.96	3.641%	$46.597	$46.60	$46.60	$46.60
Purchase #2	$208.89	7.836%	$225.2586	$225.26	$225.25	$225.30
Purchase #3	$22.59	7.198%	$24.216	$24.22	$24.20	$24.20
Purchase #4	$18.82	8.550%	$20.4291	$20.43	$20.45	$20.40
Purchase #5	$214.25	3.419%	$221.5752	$221.58	$221.60	$221.60
Purchase #6	$139.75	11.489%	$155.8059	$155.81	$155.80	$155.80
Purchase #7	$75.50	9.148%	$82.4067	$82.41	$82.40	$82.40
7 purchase totals =	$724.76		$776.2885	$776.31	$776.30	$776.30