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	$206.95	7.418%	$222.3016	$222.30	$222.30	$222.30
Purchase #2	$216.63	3.268%	$223.7095	$223.71	$223.70	$223.70
Purchase #3	$134.26	6.720%	$143.2823	$143.28	$143.30	$143.30
Purchase #4	$242.73	6.390%	$258.2404	$258.24	$258.25	$258.20
Purchase #5	$95.40	7.276%	$102.3413	$102.34	$102.35	$102.30
Purchase #6	$35.46	5.730%	$37.4919	$37.49	$37.50	$37.50
Purchase #7	$191.97	11.172%	$213.4169	$213.42	$213.40	$213.40
7 purchase totals =	$1,123.40		$1,200.7839	$1,200.78	$1,200.80	$1,200.70