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	$164.47	4.292%	$171.5291	$171.53	$171.55	$171.50
Purchase #2	$67.53	13.307%	$76.5162	$76.52	$76.50	$76.50
Purchase #3	$78.57	9.172%	$85.7764	$85.78	$85.80	$85.80
Purchase #4	$6.87	6.703%	$7.3305	$7.33	$7.35	$7.30
Purchase #5	$12.32	11.339%	$13.717	$13.72	$13.70	$13.70
Purchase #6	$113.90	11.805%	$127.3459	$127.35	$127.35	$127.30
Purchase #7	$175.57	5.581%	$185.3686	$185.37	$185.35	$185.40
7 purchase totals =	$619.23		$667.5837	$667.60	$667.60	$667.50