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	$82.46	3.830%	$85.6182	$85.62	$85.60	$85.60
Purchase #2	$142.74	4.259%	$148.8193	$148.82	$148.80	$148.80
Purchase #3	$242.67	9.194%	$264.9811	$264.98	$265.00	$265.00
Purchase #4	$102.58	9.149%	$111.965	$111.97	$111.95	$112.00
Purchase #5	$108.42	3.619%	$112.3437	$112.34	$112.35	$112.30
Purchase #6	$108.45	12.394%	$121.8913	$121.89	$121.90	$121.90
Purchase #7	$92.46	3.217%	$95.4344	$95.43	$95.45	$95.40
7 purchase totals =	$879.78		$941.0530	$941.05	$941.05	$941.00