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	$189.83	12.474%	$213.5094	$213.51	$213.50	$213.50
Purchase #2	$25.39	5.726%	$26.8438	$26.84	$26.85	$26.80
Purchase #3	$210.39	4.359%	$219.5609	$219.56	$219.55	$219.60
Purchase #4	$57.48	3.689%	$59.6004	$59.60	$59.60	$59.60
Purchase #5	$95.72	11.219%	$106.4588	$106.46	$106.45	$106.50
Purchase #6	$34.73	6.284%	$36.9124	$36.91	$36.90	$36.90
Purchase #7	$54.32	13.213%	$61.4973	$61.50	$61.50	$61.50
7 purchase totals =	$667.86		$724.3830	$724.38	$724.35	$724.40