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	$154.87	7.721%	$166.8275	$166.83	$166.85	$166.80
Purchase #2	$131.98	3.761%	$136.9438	$136.94	$136.95	$136.90
Purchase #3	$85.54	3.194%	$88.2721	$88.27	$88.25	$88.30
Purchase #4	$210.25	6.676%	$224.2863	$224.29	$224.30	$224.30
Purchase #5	$32.52	10.622%	$35.9743	$35.97	$35.95	$36.00
Purchase #6	$38.27	10.446%	$42.2677	$42.27	$42.25	$42.30
Purchase #7	$94.85	12.264%	$106.4824	$106.48	$106.50	$106.50
7 purchase totals =	$748.28		$801.0541	$801.05	$801.05	$801.10