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	$157.47	3.830%	$163.5011	$163.50	$163.50	$163.50
Purchase #2	$201.39	10.469%	$222.4735	$222.47	$222.45	$222.50
Purchase #3	$158.78	13.855%	$180.779	$180.78	$180.80	$180.80
Purchase #4	$113.93	8.629%	$123.761	$123.76	$123.75	$123.80
Purchase #5	$36.89	9.303%	$40.3219	$40.32	$40.30	$40.30
Purchase #6	$52.62	3.118%	$54.2607	$54.26	$54.25	$54.30
Purchase #7	$244.94	9.450%	$268.0868	$268.09	$268.10	$268.10
7 purchase totals =	$966.02		$1,053.1840	$1,053.18	$1,053.15	$1,053.30