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	$212.26	8.799%	$230.9368	$230.94	$230.95	$230.90
Purchase #2	$203.34	12.488%	$228.7331	$228.73	$228.75	$228.70
Purchase #3	$227.42	7.558%	$244.6084	$244.61	$244.60	$244.60
Purchase #4	$158.77	10.196%	$174.9582	$174.96	$174.95	$175.00
Purchase #5	$190.38	13.247%	$215.5996	$215.60	$215.60	$215.60
Purchase #6	$55.28	12.464%	$62.1701	$62.17	$62.15	$62.20
Purchase #7	$210.59	5.603%	$222.3894	$222.39	$222.40	$222.40
7 purchase totals =	$1,258.04		$1,379.3956	$1,379.40	$1,379.40	$1,379.40