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	$72.96	4.333%	$76.1214	$76.12	$76.10	$76.10
Purchase #2	$97.76	3.255%	$100.9421	$100.94	$100.95	$100.90
Purchase #3	$80.64	5.330%	$84.9381	$84.94	$84.95	$84.90
Purchase #4	$63.48	3.549%	$65.7329	$65.73	$65.75	$65.70
Purchase #5	$19.48	3.123%	$20.0884	$20.09	$20.10	$20.10
Purchase #6	$248.47	4.142%	$258.7616	$258.76	$258.75	$258.80
Purchase #7	$54.33	11.433%	$60.5415	$60.54	$60.55	$60.50
7 purchase totals =	$637.12		$667.1260	$667.12	$667.15	$667.00