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	$139.55	8.257%	$151.0726	$151.07	$151.05	$151.10
Purchase #2	$69.82	12.412%	$78.4861	$78.49	$78.50	$78.50
Purchase #3	$213.70	4.382%	$223.0643	$223.06	$223.05	$223.10
Purchase #4	$243.43	5.250%	$256.2101	$256.21	$256.20	$256.20
Purchase #5	$130.25	4.553%	$136.1803	$136.18	$136.20	$136.20
Purchase #6	$9.81	6.860%	$10.483	$10.48	$10.50	$10.50
Purchase #7	$92.66	4.205%	$96.5564	$96.56	$96.55	$96.60
7 purchase totals =	$899.22		$952.0528	$952.05	$952.05	$952.20