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	$185.89	10.270%	$204.9809	$204.98	$205.00	$205.00
Purchase #2	$176.32	8.140%	$190.6724	$190.67	$190.65	$190.70
Purchase #3	$34.61	9.278%	$37.8211	$37.82	$37.80	$37.80
Purchase #4	$71.34	10.221%	$78.6317	$78.63	$78.65	$78.60
Purchase #5	$125.59	12.314%	$141.0552	$141.06	$141.05	$141.10
Purchase #6	$193.79	7.130%	$207.6072	$207.61	$207.60	$207.60
Purchase #7	$144.71	5.455%	$152.6039	$152.60	$152.60	$152.60
7 purchase totals =	$932.25		$1,013.3724	$1,013.37	$1,013.35	$1,013.40