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	$116.39	4.229%	$121.3121	$121.31	$121.30	$121.30
Purchase #2	$213.99	13.374%	$242.609	$242.61	$242.60	$242.60
Purchase #3	$217.64	13.849%	$247.781	$247.78	$247.80	$247.80
Purchase #4	$148.66	4.121%	$154.7863	$154.79	$154.80	$154.80
Purchase #5	$82.81	3.459%	$85.6744	$85.67	$85.65	$85.70
Purchase #6	$209.89	7.599%	$225.8395	$225.84	$225.85	$225.80
Purchase #7	$43.46	4.863%	$45.5735	$45.57	$45.55	$45.60
7 purchase totals =	$1,032.84		$1,123.5758	$1,123.57	$1,123.55	$1,123.60