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	$43.49	3.588%	$45.0504	$45.05	$45.05	$45.10
Purchase #2	$199.58	4.600%	$208.7607	$208.76	$208.75	$208.80
Purchase #3	$46.84	12.131%	$52.5222	$52.52	$52.50	$52.50
Purchase #4	$110.37	8.235%	$119.459	$119.46	$119.45	$119.50
Purchase #5	$209.86	6.203%	$222.8776	$222.88	$222.90	$222.90
Purchase #6	$46.69	9.296%	$51.0303	$51.03	$51.05	$51.00
Purchase #7	$159.54	8.109%	$172.4771	$172.48	$172.50	$172.50
7 purchase totals =	$816.37		$872.1773	$872.18	$872.20	$872.30