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	$147.34	7.763%	$158.778	$158.78	$158.80	$158.80
Purchase #2	$144.64	12.427%	$162.6144	$162.61	$162.60	$162.60
Purchase #3	$148.57	10.402%	$164.0243	$164.02	$164.00	$164.00
Purchase #4	$32.48	10.700%	$35.9554	$35.96	$35.95	$36.00
Purchase #5	$153.46	10.437%	$169.4766	$169.48	$169.50	$169.50
Purchase #6	$73.39	13.527%	$83.3175	$83.32	$83.30	$83.30
Purchase #7	$201.70	8.752%	$219.3528	$219.35	$219.35	$219.40
7 purchase totals =	$901.58		$993.5190	$993.52	$993.50	$993.60