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	$73.42	12.127%	$82.3236	$82.32	$82.30	$82.30
Purchase #2	$57.46	5.525%	$60.6347	$60.63	$60.65	$60.60
Purchase #3	$104.29	13.648%	$118.5235	$118.52	$118.50	$118.50
Purchase #4	$10.41	4.597%	$10.8885	$10.89	$10.90	$10.90
Purchase #5	$249.47	3.111%	$257.231	$257.23	$257.25	$257.20
Purchase #6	$56.69	9.154%	$61.8794	$61.88	$61.90	$61.90
Purchase #7	$111.33	4.342%	$116.1639	$116.16	$116.15	$116.20
7 purchase totals =	$663.07		$707.6446	$707.63	$707.65	$707.60