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	$38.51	11.187%	$42.8181	$42.82	$42.80	$42.80
Purchase #2	$30.98	8.623%	$33.6514	$33.65	$33.65	$33.70
Purchase #3	$44.76	4.702%	$46.8646	$46.86	$46.85	$46.90
Purchase #4	$100.44	11.427%	$111.9173	$111.92	$111.90	$111.90
Purchase #5	$175.53	12.104%	$196.7762	$196.78	$196.80	$196.80
Purchase #6	$50.91	7.379%	$54.6666	$54.67	$54.65	$54.70
Purchase #7	$122.49	6.549%	$130.5119	$130.51	$130.50	$130.50
7 purchase totals =	$563.62		$617.2061	$617.21	$617.15	$617.30