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	$29.52	10.122%	$32.508	$32.51	$32.50	$32.50
Purchase #2	$205.81	8.588%	$223.485	$223.49	$223.50	$223.50
Purchase #3	$219.76	3.444%	$227.3285	$227.33	$227.35	$227.30
Purchase #4	$76.92	12.539%	$86.565	$86.57	$86.55	$86.60
Purchase #5	$203.48	10.648%	$225.1466	$225.15	$225.15	$225.10
Purchase #6	$109.30	13.377%	$123.9211	$123.92	$123.90	$123.90
Purchase #7	$76.80	8.161%	$83.0676	$83.07	$83.05	$83.10
7 purchase totals =	$921.59		$1,002.0218	$1,002.04	$1,002.00	$1,002.00