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	$126.40	10.534%	$139.715	$139.72	$139.70	$139.70
Purchase #2	$138.76	7.209%	$148.7632	$148.76	$148.75	$148.80
Purchase #3	$116.79	11.824%	$130.5992	$130.60	$130.60	$130.60
Purchase #4	$198.89	12.445%	$223.6419	$223.64	$223.65	$223.60
Purchase #5	$39.98	3.802%	$41.5	$41.50	$41.50	$41.50
Purchase #6	$160.46	5.434%	$169.1794	$169.18	$169.20	$169.20
Purchase #7	$231.56	3.860%	$240.4982	$240.50	$240.50	$240.50
7 purchase totals =	$1,012.84		$1,093.8969	$1,093.90	$1,093.90	$1,093.90