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	$144.65	4.321%	$150.9003	$150.90	$150.90	$150.90
Purchase #2	$117.38	7.766%	$126.4957	$126.50	$126.50	$126.50
Purchase #3	$84.56	6.700%	$90.2255	$90.23	$90.25	$90.20
Purchase #4	$101.89	6.331%	$108.3407	$108.34	$108.35	$108.30
Purchase #5	$191.31	4.475%	$199.8711	$199.87	$199.85	$199.90
Purchase #6	$211.89	6.547%	$225.7624	$225.76	$225.75	$225.80
Purchase #7	$124.63	5.246%	$131.1681	$131.17	$131.15	$131.20
7 purchase totals =	$976.31		$1,032.7638	$1,032.77	$1,032.75	$1,032.80