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	$157.56	8.486%	$170.9305	$170.93	$170.95	$170.90
Purchase #2	$89.25	3.394%	$92.2791	$92.28	$92.30	$92.30
Purchase #3	$33.61	10.592%	$37.17	$37.17	$37.15	$37.20
Purchase #4	$78.72	13.791%	$89.5763	$89.58	$89.60	$89.60
Purchase #5	$228.39	13.351%	$258.8823	$258.88	$258.90	$258.90
Purchase #6	$221.97	12.200%	$249.0503	$249.05	$249.05	$249.10
Purchase #7	$60.39	8.167%	$65.3221	$65.32	$65.30	$65.30
7 purchase totals =	$869.89		$963.2106	$963.21	$963.25	$963.30