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	$120.48	11.660%	$134.528	$134.53	$134.55	$134.50
Purchase #2	$122.55	12.533%	$137.9092	$137.91	$137.90	$137.90
Purchase #3	$109.98	3.582%	$113.9195	$113.92	$113.90	$113.90
Purchase #4	$208.76	6.503%	$222.3357	$222.34	$222.35	$222.30
Purchase #5	$201.40	11.661%	$224.8853	$224.89	$224.90	$224.90
Purchase #6	$95.50	4.871%	$100.1518	$100.15	$100.15	$100.20
Purchase #7	$144.56	9.581%	$158.4103	$158.41	$158.40	$158.40
7 purchase totals =	$1,003.23		$1,092.1398	$1,092.15	$1,092.15	$1,092.10