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	$28.34	8.529%	$30.7571	$30.76	$30.75	$30.80
Purchase #2	$30.48	11.342%	$33.937	$33.94	$33.95	$33.90
Purchase #3	$59.74	12.239%	$67.0516	$67.05	$67.05	$67.10
Purchase #4	$112.94	12.832%	$127.4325	$127.43	$127.45	$127.40
Purchase #5	$199.81	10.718%	$221.2256	$221.23	$221.25	$221.20
Purchase #6	$235.46	12.473%	$264.8289	$264.83	$264.85	$264.80
Purchase #7	$222.66	4.541%	$232.771	$232.77	$232.75	$232.80
7 purchase totals =	$889.43		$978.0037	$978.01	$978.05	$978.00