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	$91.33	7.196%	$97.9021	$97.90	$97.90	$97.90
Purchase #2	$80.34	13.391%	$91.0983	$91.10	$91.10	$91.10
Purchase #3	$40.82	5.709%	$43.1504	$43.15	$43.15	$43.20
Purchase #4	$127.63	13.635%	$145.0324	$145.03	$145.05	$145.00
Purchase #5	$235.37	6.381%	$250.389	$250.39	$250.40	$250.40
Purchase #6	$214.34	11.435%	$238.8498	$238.85	$238.85	$238.80
Purchase #7	$48.29	6.663%	$51.5076	$51.51	$51.50	$51.50
7 purchase totals =	$838.12		$917.9296	$917.93	$917.95	$917.90