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	$81.30	4.796%	$85.1991	$85.20	$85.20	$85.20
Purchase #2	$48.82	12.853%	$55.0948	$55.09	$55.10	$55.10
Purchase #3	$150.40	4.407%	$157.0281	$157.03	$157.05	$157.00
Purchase #4	$167.97	3.296%	$173.5063	$173.51	$173.50	$173.50
Purchase #5	$41.61	8.751%	$45.2513	$45.25	$45.25	$45.30
Purchase #6	$54.84	8.796%	$59.6637	$59.66	$59.65	$59.70
Purchase #7	$102.96	8.166%	$111.3677	$111.37	$111.35	$111.40
7 purchase totals =	$647.90		$687.1110	$687.11	$687.10	$687.20