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	$157.95	7.276%	$169.4424	$169.44	$169.45	$169.40
Purchase #2	$78.61	4.209%	$81.9187	$81.92	$81.90	$81.90
Purchase #3	$12.86	4.544%	$13.4444	$13.44	$13.45	$13.40
Purchase #4	$151.69	5.466%	$159.9814	$159.98	$160.00	$160.00
Purchase #5	$156.73	7.627%	$168.6838	$168.68	$168.70	$168.70
Purchase #6	$84.47	8.333%	$91.5089	$91.51	$91.50	$91.50
Purchase #7	$34.50	3.173%	$35.5947	$35.59	$35.60	$35.60
7 purchase totals =	$676.81		$720.5743	$720.56	$720.60	$720.50