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	$41.43	3.749%	$42.9832	$42.98	$43.00	$43.00
Purchase #2	$208.73	3.613%	$216.2714	$216.27	$216.25	$216.30
Purchase #3	$136.93	5.474%	$144.4255	$144.43	$144.45	$144.40
Purchase #4	$55.88	3.162%	$57.6469	$57.65	$57.65	$57.60
Purchase #5	$61.29	6.676%	$65.3817	$65.38	$65.40	$65.40
Purchase #6	$142.69	13.171%	$161.4837	$161.48	$161.50	$161.50
Purchase #7	$223.26	3.750%	$231.6323	$231.63	$231.65	$231.60
7 purchase totals =	$870.21		$919.8247	$919.82	$919.90	$919.80