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	$35.92	5.508%	$37.8985	$37.90	$37.90	$37.90
Purchase #2	$75.68	4.286%	$78.9236	$78.92	$78.90	$78.90
Purchase #3	$204.83	3.865%	$212.7467	$212.75	$212.75	$212.70
Purchase #4	$73.57	12.705%	$82.9171	$82.92	$82.90	$82.90
Purchase #5	$132.80	11.738%	$148.3881	$148.39	$148.40	$148.40
Purchase #6	$45.90	3.561%	$47.5345	$47.53	$47.55	$47.50
Purchase #7	$213.90	3.535%	$221.4614	$221.46	$221.45	$221.50
7 purchase totals =	$782.60		$829.8699	$829.87	$829.85	$829.80