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	$152.69	10.143%	$168.1773	$168.18	$168.20	$168.20
Purchase #2	$43.61	11.317%	$48.5453	$48.55	$48.55	$48.50
Purchase #3	$162.52	11.398%	$181.044	$181.04	$181.05	$181.00
Purchase #4	$77.37	11.376%	$86.1716	$86.17	$86.15	$86.20
Purchase #5	$122.36	13.670%	$139.0866	$139.09	$139.10	$139.10
Purchase #6	$97.57	3.175%	$100.6678	$100.67	$100.65	$100.70
Purchase #7	$209.61	5.847%	$221.8659	$221.87	$221.85	$221.90
7 purchase totals =	$865.73		$945.5585	$945.57	$945.55	$945.60