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	$103.89	9.215%	$113.4635	$113.46	$113.45	$113.50
Purchase #2	$28.36	5.559%	$29.9365	$29.94	$29.95	$29.90
Purchase #3	$122.56	7.208%	$131.3941	$131.39	$131.40	$131.40
Purchase #4	$52.63	7.155%	$56.3957	$56.40	$56.40	$56.40
Purchase #5	$211.38	11.474%	$235.6337	$235.63	$235.65	$235.60
Purchase #6	$177.92	7.187%	$190.7071	$190.71	$190.70	$190.70
Purchase #7	$36.98	9.178%	$40.374	$40.37	$40.35	$40.40
7 purchase totals =	$733.72		$797.9046	$797.90	$797.90	$797.90