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	$43.67	3.468%	$45.1845	$45.18	$45.20	$45.20
Purchase #2	$167.87	13.645%	$190.7759	$190.78	$190.80	$190.80
Purchase #3	$230.55	3.630%	$238.919	$238.92	$238.90	$238.90
Purchase #4	$13.27	3.722%	$13.7639	$13.76	$13.75	$13.80
Purchase #5	$187.32	7.249%	$200.8988	$200.90	$200.90	$200.90
Purchase #6	$91.31	10.314%	$100.7277	$100.73	$100.75	$100.70
Purchase #7	$128.72	5.739%	$136.1072	$136.11	$136.10	$136.10
7 purchase totals =	$862.71		$926.3770	$926.38	$926.40	$926.40