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	$250.25	6.252%	$265.8956	$265.90	$265.90	$265.90
Purchase #2	$14.48	9.294%	$15.8258	$15.83	$15.85	$15.80
Purchase #3	$39.68	5.756%	$41.964	$41.96	$41.95	$42.00
Purchase #4	$121.65	4.561%	$127.1985	$127.20	$127.20	$127.20
Purchase #5	$75.57	8.213%	$81.7766	$81.78	$81.80	$81.80
Purchase #6	$30.90	9.453%	$33.821	$33.82	$33.80	$33.80
Purchase #7	$187.78	6.188%	$199.3998	$199.40	$199.40	$199.40
7 purchase totals =	$720.31		$765.8813	$765.89	$765.90	$765.90