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	$127.78	10.611%	$141.3387	$141.34	$141.35	$141.30
Purchase #2	$161.85	6.635%	$172.5887	$172.59	$172.60	$172.60
Purchase #3	$78.74	12.530%	$88.6061	$88.61	$88.60	$88.60
Purchase #4	$127.50	7.118%	$136.5755	$136.58	$136.60	$136.60
Purchase #5	$28.40	12.736%	$32.017	$32.02	$32.00	$32.00
Purchase #6	$113.92	10.442%	$125.8155	$125.82	$125.80	$125.80
Purchase #7	$229.59	4.257%	$239.3636	$239.36	$239.35	$239.40
7 purchase totals =	$867.78		$936.3051	$936.32	$936.30	$936.30