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	$217.96	5.305%	$229.5228	$229.52	$229.50	$229.50
Purchase #2	$32.30	11.665%	$36.0678	$36.07	$36.05	$36.10
Purchase #3	$199.64	8.838%	$217.2842	$217.28	$217.30	$217.30
Purchase #4	$129.37	6.797%	$138.1633	$138.16	$138.15	$138.20
Purchase #5	$166.54	4.835%	$174.5922	$174.59	$174.60	$174.60
Purchase #6	$80.72	3.707%	$83.7123	$83.71	$83.70	$83.70
Purchase #7	$240.34	3.421%	$248.562	$248.56	$248.55	$248.60
7 purchase totals =	$1,066.87		$1,127.9046	$1,127.89	$1,127.85	$1,128.00