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	$216.59	4.166%	$225.6131	$225.61	$225.60	$225.60
Purchase #2	$126.63	3.459%	$131.0101	$131.01	$131.00	$131.00
Purchase #3	$38.78	13.836%	$44.1456	$44.15	$44.15	$44.10
Purchase #4	$168.27	8.362%	$182.3407	$182.34	$182.35	$182.30
Purchase #5	$136.99	10.747%	$151.7123	$151.71	$151.70	$151.70
Purchase #6	$96.34	9.863%	$105.842	$105.84	$105.85	$105.80
Purchase #7	$101.37	11.110%	$112.6322	$112.63	$112.65	$112.60
7 purchase totals =	$884.97		$953.2960	$953.29	$953.30	$953.10