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	$139.51	9.565%	$152.8541	$152.85	$152.85	$152.90
Purchase #2	$148.93	5.605%	$157.2775	$157.28	$157.30	$157.30
Purchase #3	$227.53	5.873%	$240.8928	$240.89	$240.90	$240.90
Purchase #4	$150.98	3.629%	$156.4591	$156.46	$156.45	$156.50
Purchase #5	$35.46	5.136%	$37.2812	$37.28	$37.30	$37.30
Purchase #6	$74.75	11.771%	$83.5488	$83.55	$83.55	$83.50
Purchase #7	$184.62	10.214%	$203.4771	$203.48	$203.50	$203.50
7 purchase totals =	$961.78		$1,031.7906	$1,031.79	$1,031.85	$1,031.90