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	$40.36	4.866%	$42.3239	$42.32	$42.30	$42.30
Purchase #2	$11.49	6.577%	$12.2457	$12.25	$12.25	$12.20
Purchase #3	$61.88	3.321%	$63.935	$63.94	$63.95	$63.90
Purchase #4	$247.90	10.623%	$274.2344	$274.23	$274.25	$274.20
Purchase #5	$208.54	6.756%	$222.629	$222.63	$222.65	$222.60
Purchase #6	$157.55	3.440%	$162.9697	$162.97	$162.95	$163.00
Purchase #7	$119.73	3.108%	$123.4512	$123.45	$123.45	$123.50
7 purchase totals =	$847.45		$901.7889	$901.79	$901.80	$901.70