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	$222.53	12.270%	$249.8344	$249.83	$249.85	$249.80
Purchase #2	$71.34	8.615%	$77.4859	$77.49	$77.50	$77.50
Purchase #3	$228.37	5.671%	$241.3209	$241.32	$241.30	$241.30
Purchase #4	$31.82	4.697%	$33.3146	$33.31	$33.30	$33.30
Purchase #5	$169.54	6.467%	$180.5042	$180.50	$180.50	$180.50
Purchase #6	$65.33	7.287%	$70.0906	$70.09	$70.10	$70.10
Purchase #7	$229.65	8.327%	$248.773	$248.77	$248.75	$248.80
7 purchase totals =	$1,018.58		$1,101.3236	$1,101.31	$1,101.30	$1,101.30