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	$60.83	10.646%	$67.306	$67.31	$67.30	$67.30
Purchase #2	$33.36	6.484%	$35.5231	$35.52	$35.50	$35.50
Purchase #3	$170.40	6.817%	$182.0162	$182.02	$182.00	$182.00
Purchase #4	$122.36	11.468%	$136.3922	$136.39	$136.40	$136.40
Purchase #5	$212.27	13.131%	$240.1432	$240.14	$240.15	$240.10
Purchase #6	$27.67	13.357%	$31.3659	$31.37	$31.35	$31.40
Purchase #7	$112.26	13.166%	$127.0402	$127.04	$127.05	$127.00
7 purchase totals =	$739.15		$819.7868	$819.79	$819.75	$819.70