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	$142.65	7.450%	$153.2774	$153.28	$153.30	$153.30
Purchase #2	$92.83	13.626%	$105.479	$105.48	$105.50	$105.50
Purchase #3	$76.96	6.274%	$81.7885	$81.79	$81.80	$81.80
Purchase #4	$81.28	7.293%	$87.2078	$87.21	$87.20	$87.20
Purchase #5	$138.67	8.819%	$150.8993	$150.90	$150.90	$150.90
Purchase #6	$9.96	5.238%	$10.4817	$10.48	$10.50	$10.50
Purchase #7	$72.66	7.460%	$78.0804	$78.08	$78.10	$78.10
7 purchase totals =	$615.01		$667.2141	$667.22	$667.30	$667.30