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	$137.55	10.421%	$151.8841	$151.88	$151.90	$151.90
Purchase #2	$42.83	4.344%	$44.6905	$44.69	$44.70	$44.70
Purchase #3	$139.38	3.865%	$144.767	$144.77	$144.75	$144.80
Purchase #4	$199.98	9.871%	$219.72	$219.72	$219.70	$219.70
Purchase #5	$179.47	6.854%	$191.7709	$191.77	$191.75	$191.80
Purchase #6	$52.43	13.339%	$59.4236	$59.42	$59.40	$59.40
Purchase #7	$140.35	9.380%	$153.5148	$153.51	$153.50	$153.50
7 purchase totals =	$891.99		$965.7709	$965.76	$965.70	$965.80