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	$36.99	9.339%	$40.4445	$40.44	$40.45	$40.40
Purchase #2	$92.54	10.536%	$102.29	$102.29	$102.30	$102.30
Purchase #3	$119.89	12.482%	$134.8547	$134.85	$134.85	$134.90
Purchase #4	$29.92	4.821%	$31.3624	$31.36	$31.35	$31.40
Purchase #5	$37.85	4.774%	$39.657	$39.66	$39.65	$39.70
Purchase #6	$35.50	4.323%	$37.0347	$37.03	$37.05	$37.00
Purchase #7	$72.61	5.366%	$76.5063	$76.51	$76.50	$76.50
7 purchase totals =	$425.30		$462.1496	$462.14	$462.15	$462.20