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	$182.53	7.626%	$196.4497	$196.45	$196.45	$196.40
Purchase #2	$35.87	10.144%	$39.5087	$39.51	$39.50	$39.50
Purchase #3	$133.36	10.124%	$146.8614	$146.86	$146.85	$146.90
Purchase #4	$81.40	7.300%	$87.3422	$87.34	$87.35	$87.30
Purchase #5	$166.95	8.394%	$180.9638	$180.96	$180.95	$181.00
Purchase #6	$82.67	3.233%	$85.3427	$85.34	$85.35	$85.30
Purchase #7	$71.25	13.257%	$80.6956	$80.70	$80.70	$80.70
7 purchase totals =	$754.03		$817.1641	$817.16	$817.15	$817.10