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	$68.37	11.702%	$76.3707	$76.37	$76.35	$76.40
Purchase #2	$128.50	13.252%	$145.5288	$145.53	$145.55	$145.50
Purchase #3	$74.77	10.224%	$82.4145	$82.41	$82.40	$82.40
Purchase #4	$65.79	10.551%	$72.7315	$72.73	$72.75	$72.70
Purchase #5	$33.98	4.199%	$35.4068	$35.41	$35.40	$35.40
Purchase #6	$173.28	5.580%	$182.949	$182.95	$182.95	$182.90
Purchase #7	$35.96	4.528%	$37.5883	$37.59	$37.60	$37.60
7 purchase totals =	$580.65		$632.9896	$632.99	$633.00	$632.90