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	$161.57	7.352%	$173.4486	$173.45	$173.45	$173.40
Purchase #2	$105.61	8.213%	$114.2837	$114.28	$114.30	$114.30
Purchase #3	$172.47	4.303%	$179.8914	$179.89	$179.90	$179.90
Purchase #4	$31.84	11.377%	$35.4624	$35.46	$35.45	$35.50
Purchase #5	$11.84	7.458%	$12.723	$12.72	$12.70	$12.70
Purchase #6	$103.42	5.220%	$108.8185	$108.82	$108.80	$108.80
Purchase #7	$6.98	13.777%	$7.9416	$7.94	$7.95	$7.90
7 purchase totals =	$593.73		$632.5692	$632.56	$632.55	$632.50