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	$157.49	9.715%	$172.7902	$172.79	$172.80	$172.80
Purchase #2	$77.65	9.551%	$85.0664	$85.07	$85.05	$85.10
Purchase #3	$106.73	8.583%	$115.8906	$115.89	$115.90	$115.90
Purchase #4	$167.96	10.473%	$185.5505	$185.55	$185.55	$185.60
Purchase #5	$205.26	13.533%	$233.0378	$233.04	$233.05	$233.00
Purchase #6	$234.47	11.130%	$260.5665	$260.57	$260.55	$260.60
Purchase #7	$68.29	9.192%	$74.5672	$74.57	$74.55	$74.60
7 purchase totals =	$1,017.85		$1,127.4692	$1,127.48	$1,127.45	$1,127.60