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	$35.50	6.232%	$37.7124	$37.71	$37.70	$37.70
Purchase #2	$204.80	11.197%	$227.7315	$227.73	$227.75	$227.70
Purchase #3	$195.56	7.314%	$209.8633	$209.86	$209.85	$209.90
Purchase #4	$152.85	7.664%	$164.5644	$164.56	$164.55	$164.60
Purchase #5	$172.55	9.762%	$189.3943	$189.39	$189.40	$189.40
Purchase #6	$197.68	7.190%	$211.8932	$211.89	$211.90	$211.90
Purchase #7	$158.40	8.729%	$172.2267	$172.23	$172.25	$172.20
7 purchase totals =	$1,117.34		$1,213.3858	$1,213.37	$1,213.40	$1,213.40