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	$90.47	11.822%	$101.1654	$101.17	$101.15	$101.20
Purchase #2	$122.84	11.874%	$137.426	$137.43	$137.45	$137.40
Purchase #3	$247.84	7.233%	$265.7663	$265.77	$265.75	$265.80
Purchase #4	$85.98	3.865%	$89.3031	$89.30	$89.30	$89.30
Purchase #5	$234.69	3.366%	$242.5897	$242.59	$242.60	$242.60
Purchase #6	$150.52	6.637%	$160.51	$160.51	$160.50	$160.50
Purchase #7	$233.87	12.666%	$263.492	$263.49	$263.50	$263.50
7 purchase totals =	$1,166.21		$1,260.2525	$1,260.26	$1,260.25	$1,260.30