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	$209.46	5.216%	$220.3854	$220.39	$220.40	$220.40
Purchase #2	$24.32	4.647%	$25.4502	$25.45	$25.45	$25.50
Purchase #3	$68.28	5.457%	$72.006	$72.01	$72.00	$72.00
Purchase #4	$82.30	9.207%	$89.8774	$89.88	$89.90	$89.90
Purchase #5	$92.38	9.731%	$101.3695	$101.37	$101.35	$101.40
Purchase #6	$36.63	3.544%	$37.9282	$37.93	$37.95	$37.90
Purchase #7	$150.34	3.591%	$155.7387	$155.74	$155.75	$155.70
7 purchase totals =	$663.71		$702.7554	$702.77	$702.80	$702.80