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	$74.91	9.820%	$82.2662	$82.27	$82.25	$82.30
Purchase #2	$105.38	7.659%	$113.4511	$113.45	$113.45	$113.50
Purchase #3	$192.37	9.646%	$210.926	$210.93	$210.95	$210.90
Purchase #4	$72.55	3.274%	$74.9253	$74.93	$74.95	$74.90
Purchase #5	$170.39	4.821%	$178.6045	$178.60	$178.60	$178.60
Purchase #6	$135.45	11.410%	$150.9048	$150.90	$150.90	$150.90
Purchase #7	$198.77	7.358%	$213.3955	$213.40	$213.40	$213.40
7 purchase totals =	$949.82		$1,024.4734	$1,024.48	$1,024.50	$1,024.50