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	$49.74	9.140%	$54.2862	$54.29	$54.30	$54.30
Purchase #2	$12.67	13.873%	$14.4277	$14.43	$14.45	$14.40
Purchase #3	$136.88	4.142%	$142.5496	$142.55	$142.55	$142.50
Purchase #4	$89.59	12.871%	$101.1211	$101.12	$101.10	$101.10
Purchase #5	$33.95	9.853%	$37.2951	$37.30	$37.30	$37.30
Purchase #6	$168.96	8.583%	$183.4618	$183.46	$183.45	$183.50
Purchase #7	$82.37	12.308%	$92.5081	$92.51	$92.50	$92.50
7 purchase totals =	$574.16		$625.6496	$625.66	$625.65	$625.60