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	$138.61	9.262%	$151.4481	$151.45	$151.45	$151.40
Purchase #2	$39.71	9.319%	$43.4106	$43.41	$43.40	$43.40
Purchase #3	$65.82	9.663%	$72.1802	$72.18	$72.20	$72.20
Purchase #4	$52.34	4.499%	$54.6948	$54.69	$54.70	$54.70
Purchase #5	$207.49	9.831%	$227.8883	$227.89	$227.90	$227.90
Purchase #6	$130.57	8.727%	$141.9648	$141.96	$141.95	$142.00
Purchase #7	$80.73	7.624%	$86.8849	$86.88	$86.90	$86.90
7 purchase totals =	$715.27		$778.4717	$778.46	$778.50	$778.50