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	$107.60	4.521%	$112.4646	$112.46	$112.45	$112.50
Purchase #2	$40.48	4.134%	$42.1534	$42.15	$42.15	$42.20
Purchase #3	$31.53	12.654%	$35.5198	$35.52	$35.50	$35.50
Purchase #4	$84.80	5.109%	$89.1324	$89.13	$89.15	$89.10
Purchase #5	$130.79	4.133%	$136.1956	$136.20	$136.20	$136.20
Purchase #6	$169.76	13.364%	$192.4467	$192.45	$192.45	$192.40
Purchase #7	$173.64	11.700%	$193.9559	$193.96	$193.95	$194.00
7 purchase totals =	$738.60		$801.8684	$801.87	$801.85	$801.90