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	$198.81	4.384%	$207.5258	$207.53	$207.55	$207.50
Purchase #2	$55.57	11.571%	$62	$62.00	$62.00	$62.00
Purchase #3	$100.63	6.247%	$106.9164	$106.92	$106.90	$106.90
Purchase #4	$30.52	13.820%	$34.7379	$34.74	$34.75	$34.70
Purchase #5	$71.90	11.315%	$80.0355	$80.04	$80.05	$80.00
Purchase #6	$35.62	4.232%	$37.1274	$37.13	$37.15	$37.10
Purchase #7	$124.79	11.611%	$139.2794	$139.28	$139.30	$139.30
7 purchase totals =	$617.84		$667.6224	$667.64	$667.70	$667.50