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	$147.85	11.504%	$164.8587	$164.86	$164.85	$164.90
Purchase #2	$109.96	6.343%	$116.9348	$116.93	$116.95	$116.90
Purchase #3	$220.69	11.301%	$245.6302	$245.63	$245.65	$245.60
Purchase #4	$64.62	3.564%	$66.9231	$66.92	$66.90	$66.90
Purchase #5	$74.33	4.779%	$77.8822	$77.88	$77.90	$77.90
Purchase #6	$118.36	7.735%	$127.5151	$127.52	$127.50	$127.50
Purchase #7	$90.56	8.143%	$97.9343	$97.93	$97.95	$97.90
7 purchase totals =	$826.37		$897.6784	$897.67	$897.70	$897.60