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	$116.48	6.353%	$123.88	$123.88	$123.90	$123.90
Purchase #2	$55.25	9.731%	$60.6264	$60.63	$60.65	$60.60
Purchase #3	$239.66	5.701%	$253.323	$253.32	$253.30	$253.30
Purchase #4	$136.65	13.104%	$154.5566	$154.56	$154.55	$154.60
Purchase #5	$34.93	10.517%	$38.6036	$38.60	$38.60	$38.60
Purchase #6	$190.64	12.839%	$215.1163	$215.12	$215.10	$215.10
Purchase #7	$85.92	9.671%	$94.2293	$94.23	$94.25	$94.20
7 purchase totals =	$859.53		$940.3352	$940.34	$940.35	$940.30