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	$34.49	3.650%	$35.7489	$35.75	$35.75	$35.70
Purchase #2	$172.50	8.717%	$187.5368	$187.54	$187.55	$187.50
Purchase #3	$169.89	10.266%	$187.3309	$187.33	$187.35	$187.30
Purchase #4	$108.63	8.856%	$118.2503	$118.25	$118.25	$118.30
Purchase #5	$233.93	7.642%	$251.8069	$251.81	$251.80	$251.80
Purchase #6	$16.79	11.744%	$18.7618	$18.76	$18.75	$18.80
Purchase #7	$56.73	5.570%	$59.8899	$59.89	$59.90	$59.90
7 purchase totals =	$792.96		$859.3255	$859.33	$859.35	$859.30