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	$131.39	9.664%	$144.0875	$144.09	$144.10	$144.10
Purchase #2	$247.62	5.660%	$261.6353	$261.64	$261.65	$261.60
Purchase #3	$174.90	8.155%	$189.1631	$189.16	$189.15	$189.20
Purchase #4	$142.59	6.203%	$151.4349	$151.43	$151.45	$151.40
Purchase #5	$139.76	11.181%	$155.3866	$155.39	$155.40	$155.40
Purchase #6	$14.34	8.667%	$15.5828	$15.58	$15.60	$15.60
Purchase #7	$88.91	5.149%	$93.488	$93.49	$93.50	$93.50
7 purchase totals =	$939.51		$1,010.7782	$1,010.78	$1,010.85	$1,010.80