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	$116.36	3.478%	$120.407	$120.41	$120.40	$120.40
Purchase #2	$91.47	13.784%	$104.0782	$104.08	$104.10	$104.10
Purchase #3	$175.73	11.737%	$196.3554	$196.36	$196.35	$196.40
Purchase #4	$214.25	5.302%	$225.6095	$225.61	$225.60	$225.60
Purchase #5	$171.44	6.134%	$181.9561	$181.96	$181.95	$182.00
Purchase #6	$151.57	12.760%	$170.9103	$170.91	$170.90	$170.90
Purchase #7	$111.68	10.812%	$123.7548	$123.75	$123.75	$123.80
7 purchase totals =	$1,032.50		$1,123.0713	$1,123.08	$1,123.05	$1,123.20