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	$143.96	4.817%	$150.8946	$150.89	$150.90	$150.90
Purchase #2	$247.98	11.258%	$275.8976	$275.90	$275.90	$275.90
Purchase #3	$189.29	10.816%	$209.7636	$209.76	$209.75	$209.80
Purchase #4	$234.94	10.139%	$258.7606	$258.76	$258.75	$258.80
Purchase #5	$157.66	9.341%	$172.387	$172.39	$172.40	$172.40
Purchase #6	$146.71	3.682%	$152.1119	$152.11	$152.10	$152.10
Purchase #7	$92.95	10.823%	$103.01	$103.01	$103.00	$103.00
7 purchase totals =	$1,213.49		$1,322.8253	$1,322.82	$1,322.80	$1,322.90