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	$33.82	3.749%	$35.0879	$35.09	$35.10	$35.10
Purchase #2	$142.51	10.665%	$157.7087	$157.71	$157.70	$157.70
Purchase #3	$90.39	9.640%	$99.1036	$99.10	$99.10	$99.10
Purchase #4	$66.34	9.722%	$72.7896	$72.79	$72.80	$72.80
Purchase #5	$198.55	11.247%	$220.8809	$220.88	$220.90	$220.90
Purchase #6	$235.35	11.855%	$263.2507	$263.25	$263.25	$263.30
Purchase #7	$117.96	8.217%	$127.6528	$127.65	$127.65	$127.70
7 purchase totals =	$884.92		$976.4742	$976.47	$976.50	$976.60