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	$116.83	12.566%	$131.5109	$131.51	$131.50	$131.50
Purchase #2	$109.32	9.119%	$119.2889	$119.29	$119.30	$119.30
Purchase #3	$169.97	4.697%	$177.9535	$177.95	$177.95	$178.00
Purchase #4	$198.83	11.837%	$222.3655	$222.37	$222.35	$222.40
Purchase #5	$180.45	7.640%	$194.2364	$194.24	$194.25	$194.20
Purchase #6	$133.74	9.749%	$146.7783	$146.78	$146.80	$146.80
Purchase #7	$83.38	11.261%	$92.7694	$92.77	$92.75	$92.80
7 purchase totals =	$992.52		$1,084.9029	$1,084.91	$1,084.90	$1,085.00