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	$5.66	4.707%	$5.9264	$5.93	$5.95	$5.90
Purchase #2	$189.26	3.584%	$196.0431	$196.04	$196.05	$196.00
Purchase #3	$159.47	8.244%	$172.6167	$172.62	$172.60	$172.60
Purchase #4	$53.47	11.589%	$59.6666	$59.67	$59.65	$59.70
Purchase #5	$33.85	3.464%	$35.0226	$35.02	$35.00	$35.00
Purchase #6	$207.63	12.688%	$233.9741	$233.97	$233.95	$234.00
Purchase #7	$187.94	9.246%	$205.3169	$205.32	$205.30	$205.30
7 purchase totals =	$837.28		$908.5664	$908.57	$908.50	$908.50