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	$108.69	10.540%	$120.1459	$120.15	$120.15	$120.10
Purchase #2	$102.27	3.301%	$105.6459	$105.65	$105.65	$105.60
Purchase #3	$11.31	10.812%	$12.5328	$12.53	$12.55	$12.50
Purchase #4	$35.48	10.277%	$39.1263	$39.13	$39.15	$39.10
Purchase #5	$209.69	5.828%	$221.9107	$221.91	$221.90	$221.90
Purchase #6	$213.65	11.389%	$237.9826	$237.98	$238.00	$238.00
Purchase #7	$152.61	7.600%	$164.2084	$164.21	$164.20	$164.20
7 purchase totals =	$833.70		$901.5526	$901.56	$901.60	$901.40