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	$43.89	13.253%	$49.7067	$49.71	$49.70	$49.70
Purchase #2	$84.63	7.650%	$91.1042	$91.10	$91.10	$91.10
Purchase #3	$161.89	3.496%	$167.5497	$167.55	$167.55	$167.50
Purchase #4	$96.29	13.294%	$109.0908	$109.09	$109.10	$109.10
Purchase #5	$136.47	11.268%	$151.8474	$151.85	$151.85	$151.80
Purchase #6	$222.43	11.498%	$248.005	$248.01	$248.00	$248.00
Purchase #7	$7.92	4.249%	$8.2565	$8.26	$8.25	$8.30
7 purchase totals =	$753.52		$825.5603	$825.57	$825.55	$825.50