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	$63.84	11.517%	$71.1925	$71.19	$71.20	$71.20
Purchase #2	$184.45	4.294%	$192.3703	$192.37	$192.35	$192.40
Purchase #3	$191.29	13.518%	$217.1486	$217.15	$217.15	$217.10
Purchase #4	$190.64	11.666%	$212.8801	$212.88	$212.90	$212.90
Purchase #5	$70.34	8.177%	$76.0917	$76.09	$76.10	$76.10
Purchase #6	$141.62	4.776%	$148.3838	$148.38	$148.40	$148.40
Purchase #7	$175.38	12.208%	$196.7904	$196.79	$196.80	$196.80
7 purchase totals =	$1,017.56		$1,114.8574	$1,114.85	$1,114.90	$1,114.90