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	$199.53	11.511%	$222.4979	$222.50	$222.50	$222.50
Purchase #2	$32.87	9.281%	$35.9207	$35.92	$35.90	$35.90
Purchase #3	$249.73	10.867%	$276.8682	$276.87	$276.85	$276.90
Purchase #4	$90.63	13.417%	$102.7898	$102.79	$102.80	$102.80
Purchase #5	$70.82	9.543%	$77.5784	$77.58	$77.60	$77.60
Purchase #6	$227.37	4.683%	$238.0177	$238.02	$238.00	$238.00
Purchase #7	$192.65	4.294%	$200.9224	$200.92	$200.90	$200.90
7 purchase totals =	$1,063.60		$1,154.5951	$1,154.60	$1,154.55	$1,154.60