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	$106.73	7.260%	$114.4786	$114.48	$114.50	$114.50
Purchase #2	$87.96	5.267%	$92.5929	$92.59	$92.60	$92.60
Purchase #3	$149.65	5.539%	$157.9391	$157.94	$157.95	$157.90
Purchase #4	$221.98	11.553%	$247.6253	$247.63	$247.65	$247.60
Purchase #5	$9.86	7.630%	$10.6123	$10.61	$10.60	$10.60
Purchase #6	$186.69	5.382%	$196.7377	$196.74	$196.75	$196.70
Purchase #7	$113.62	12.506%	$127.8293	$127.83	$127.85	$127.80
7 purchase totals =	$876.49		$947.8152	$947.82	$947.90	$947.70