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	$98.74	4.130%	$102.818	$102.82	$102.80	$102.80
Purchase #2	$188.31	9.313%	$205.8473	$205.85	$205.85	$205.80
Purchase #3	$31.46	4.363%	$32.8326	$32.83	$32.85	$32.80
Purchase #4	$113.27	5.464%	$119.4591	$119.46	$119.45	$119.50
Purchase #5	$93.37	13.266%	$105.7565	$105.76	$105.75	$105.80
Purchase #6	$155.63	9.469%	$170.3666	$170.37	$170.35	$170.40
Purchase #7	$33.48	8.186%	$36.2207	$36.22	$36.20	$36.20
7 purchase totals =	$714.26		$773.3008	$773.31	$773.25	$773.30