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	$43.58	6.787%	$46.5378	$46.54	$46.55	$46.50
Purchase #2	$38.83	3.690%	$40.2628	$40.26	$40.25	$40.30
Purchase #3	$5.89	13.206%	$6.6678	$6.67	$6.65	$6.70
Purchase #4	$173.48	13.498%	$196.8963	$196.90	$196.90	$196.90
Purchase #5	$51.70	6.514%	$55.0677	$55.07	$55.05	$55.10
Purchase #6	$5.44	13.620%	$6.1809	$6.18	$6.20	$6.20
Purchase #7	$238.42	5.251%	$250.9394	$250.94	$250.95	$250.90
7 purchase totals =	$557.34		$602.5527	$602.56	$602.55	$602.60