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	$60.40	11.697%	$67.465	$67.47	$67.45	$67.50
Purchase #2	$235.84	11.191%	$262.2329	$262.23	$262.25	$262.20
Purchase #3	$236.93	9.459%	$259.3412	$259.34	$259.35	$259.30
Purchase #4	$31.39	13.222%	$35.5404	$35.54	$35.55	$35.50
Purchase #5	$151.91	12.826%	$171.394	$171.39	$171.40	$171.40
Purchase #6	$202.50	7.571%	$217.8313	$217.83	$217.85	$217.80
Purchase #7	$40.63	11.298%	$45.2204	$45.22	$45.20	$45.20
7 purchase totals =	$959.60		$1,059.0252	$1,059.02	$1,059.05	$1,058.90