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	$121.53	9.136%	$132.633	$132.63	$132.65	$132.60
Purchase #2	$36.58	12.750%	$41.244	$41.24	$41.25	$41.20
Purchase #3	$175.94	7.166%	$188.5479	$188.55	$188.55	$188.50
Purchase #4	$211.79	4.750%	$221.85	$221.85	$221.85	$221.90
Purchase #5	$49.71	4.415%	$51.9047	$51.90	$51.90	$51.90
Purchase #6	$69.60	12.861%	$78.5513	$78.55	$78.55	$78.60
Purchase #7	$212.67	5.223%	$223.7778	$223.78	$223.80	$223.80
7 purchase totals =	$877.82		$938.5087	$938.50	$938.55	$938.50