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	$213.32	10.566%	$235.8594	$235.86	$235.85	$235.90
Purchase #2	$52.38	13.220%	$59.3046	$59.30	$59.30	$59.30
Purchase #3	$66.92	10.497%	$73.9446	$73.94	$73.95	$73.90
Purchase #4	$154.99	11.348%	$172.5783	$172.58	$172.60	$172.60
Purchase #5	$35.78	6.216%	$38.0041	$38.00	$38.00	$38.00
Purchase #6	$129.95	11.190%	$144.4914	$144.49	$144.50	$144.50
Purchase #7	$139.83	12.165%	$156.8403	$156.84	$156.85	$156.80
7 purchase totals =	$793.17		$881.0227	$881.01	$881.05	$881.00