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	$93.45	10.686%	$103.4361	$103.44	$103.45	$103.40
Purchase #2	$74.46	3.795%	$77.2858	$77.29	$77.30	$77.30
Purchase #3	$209.79	8.111%	$226.8061	$226.81	$226.80	$226.80
Purchase #4	$101.92	9.472%	$111.5739	$111.57	$111.55	$111.60
Purchase #5	$78.75	8.482%	$85.4296	$85.43	$85.45	$85.40
Purchase #6	$44.31	6.118%	$47.0209	$47.02	$47.00	$47.00
Purchase #7	$101.91	9.586%	$111.6791	$111.68	$111.70	$111.70
7 purchase totals =	$704.59		$763.2315	$763.24	$763.25	$763.20