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	$34.29	11.746%	$38.3177	$38.32	$38.30	$38.30
Purchase #2	$244.59	11.686%	$273.1728	$273.17	$273.15	$273.20
Purchase #3	$173.81	10.186%	$191.5143	$191.51	$191.50	$191.50
Purchase #4	$83.33	12.262%	$93.5479	$93.55	$93.55	$93.50
Purchase #5	$153.83	8.281%	$166.5687	$166.57	$166.55	$166.60
Purchase #6	$146.85	5.193%	$154.4759	$154.48	$154.50	$154.50
Purchase #7	$119.66	6.294%	$127.1914	$127.19	$127.20	$127.20
7 purchase totals =	$956.36		$1,044.7887	$1,044.79	$1,044.75	$1,044.80