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	$89.71	8.292%	$97.1488	$97.15	$97.15	$97.10
Purchase #2	$142.69	11.605%	$159.2492	$159.25	$159.25	$159.20
Purchase #3	$213.91	7.715%	$230.4132	$230.41	$230.40	$230.40
Purchase #4	$236.31	8.653%	$256.7579	$256.76	$256.75	$256.80
Purchase #5	$37.50	13.540%	$42.5775	$42.58	$42.60	$42.60
Purchase #6	$218.50	9.602%	$239.4804	$239.48	$239.50	$239.50
Purchase #7	$93.35	5.339%	$98.334	$98.33	$98.35	$98.30
7 purchase totals =	$1,031.97		$1,123.9610	$1,123.96	$1,124.00	$1,123.90