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	$164.92	6.619%	$175.8361	$175.84	$175.85	$175.80
Purchase #2	$210.43	5.610%	$222.2351	$222.24	$222.25	$222.20
Purchase #3	$231.45	10.542%	$255.8495	$255.85	$255.85	$255.80
Purchase #4	$78.32	4.339%	$81.7183	$81.72	$81.70	$81.70
Purchase #5	$102.74	5.701%	$108.5972	$108.60	$108.60	$108.60
Purchase #6	$250.33	12.352%	$281.2508	$281.25	$281.25	$281.30
Purchase #7	$90.76	5.268%	$95.5412	$95.54	$95.55	$95.50
7 purchase totals =	$1,128.95		$1,221.0282	$1,221.04	$1,221.05	$1,220.90