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	$152.66	6.592%	$162.7233	$162.72	$162.70	$162.70
Purchase #2	$125.77	11.484%	$140.2134	$140.21	$140.20	$140.20
Purchase #3	$227.85	6.586%	$242.8562	$242.86	$242.85	$242.90
Purchase #4	$95.89	6.776%	$102.3875	$102.39	$102.40	$102.40
Purchase #5	$186.51	4.593%	$195.0764	$195.08	$195.10	$195.10
Purchase #6	$37.97	6.739%	$40.5288	$40.53	$40.55	$40.50
Purchase #7	$219.67	3.508%	$227.376	$227.38	$227.40	$227.40
7 purchase totals =	$1,046.32		$1,111.1616	$1,111.17	$1,111.20	$1,111.20