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	$210.69	10.341%	$232.4775	$232.48	$232.50	$232.50
Purchase #2	$182.64	5.527%	$192.7345	$192.73	$192.75	$192.70
Purchase #3	$226.71	12.740%	$255.5929	$255.59	$255.60	$255.60
Purchase #4	$243.70	12.267%	$273.5947	$273.59	$273.60	$273.60
Purchase #5	$54.88	12.284%	$61.6215	$61.62	$61.60	$61.60
Purchase #6	$144.85	4.203%	$150.938	$150.94	$150.95	$150.90
Purchase #7	$140.80	12.389%	$158.2437	$158.24	$158.25	$158.20
7 purchase totals =	$1,204.27		$1,325.2028	$1,325.19	$1,325.25	$1,325.10