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	$93.39	11.211%	$103.86	$103.86	$103.85	$103.90
Purchase #2	$39.93	13.857%	$45.4631	$45.46	$45.45	$45.50
Purchase #3	$157.67	6.770%	$168.3443	$168.34	$168.35	$168.30
Purchase #4	$81.41	12.261%	$91.3917	$91.39	$91.40	$91.40
Purchase #5	$21.90	13.474%	$24.8508	$24.85	$24.85	$24.90
Purchase #6	$103.54	9.449%	$113.3235	$113.32	$113.30	$113.30
Purchase #7	$11.83	13.578%	$13.4363	$13.44	$13.45	$13.40
7 purchase totals =	$509.67		$560.6697	$560.66	$560.65	$560.70