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	$208.69	13.828%	$237.5477	$237.55	$237.55	$237.50
Purchase #2	$61.85	9.700%	$67.8495	$67.85	$67.85	$67.80
Purchase #3	$204.66	8.250%	$221.5445	$221.54	$221.55	$221.50
Purchase #4	$33.49	12.672%	$37.7339	$37.73	$37.75	$37.70
Purchase #5	$138.54	4.347%	$144.5623	$144.56	$144.55	$144.60
Purchase #6	$86.77	3.764%	$90.036	$90.04	$90.05	$90.00
Purchase #7	$231.90	13.675%	$263.6123	$263.61	$263.60	$263.60
7 purchase totals =	$965.90		$1,062.8862	$1,062.88	$1,062.90	$1,062.70