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	$22.60	4.274%	$23.5659	$23.57	$23.55	$23.60
Purchase #2	$54.75	5.247%	$57.6227	$57.62	$57.60	$57.60
Purchase #3	$153.82	11.638%	$171.7216	$171.72	$171.70	$171.70
Purchase #4	$220.50	10.507%	$243.6679	$243.67	$243.65	$243.70
Purchase #5	$150.32	8.145%	$162.5636	$162.56	$162.55	$162.60
Purchase #6	$6.76	6.490%	$7.1987	$7.20	$7.20	$7.20
Purchase #7	$42.52	7.767%	$45.8225	$45.82	$45.80	$45.80
7 purchase totals =	$651.27		$712.1629	$712.16	$712.05	$712.20