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	$217.71	7.420%	$233.8641	$233.86	$233.85	$233.90
Purchase #2	$9.95	12.200%	$11.1639	$11.16	$11.15	$11.20
Purchase #3	$155.90	6.408%	$165.8901	$165.89	$165.90	$165.90
Purchase #4	$126.39	3.787%	$131.1764	$131.18	$131.20	$131.20
Purchase #5	$74.44	13.298%	$84.339	$84.34	$84.35	$84.30
Purchase #6	$241.76	12.859%	$272.8479	$272.85	$272.85	$272.80
Purchase #7	$90.98	10.392%	$100.4346	$100.43	$100.45	$100.40
7 purchase totals =	$917.13		$999.7160	$999.71	$999.75	$999.70