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	$9.52	9.343%	$10.4095	$10.41	$10.40	$10.40
Purchase #2	$225.26	11.119%	$250.3067	$250.31	$250.30	$250.30
Purchase #3	$150.77	3.538%	$156.1042	$156.10	$156.10	$156.10
Purchase #4	$171.86	7.365%	$184.5175	$184.52	$184.50	$184.50
Purchase #5	$130.87	10.387%	$144.4635	$144.46	$144.45	$144.50
Purchase #6	$33.29	8.248%	$36.0358	$36.04	$36.05	$36.00
Purchase #7	$202.82	7.260%	$217.5447	$217.54	$217.55	$217.50
7 purchase totals =	$924.39		$999.3819	$999.38	$999.35	$999.30