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	$120.92	10.348%	$133.4328	$133.43	$133.45	$133.40
Purchase #2	$21.47	4.515%	$22.4394	$22.44	$22.45	$22.40
Purchase #3	$32.54	5.609%	$34.3652	$34.37	$34.35	$34.40
Purchase #4	$42.55	11.146%	$47.2926	$47.29	$47.30	$47.30
Purchase #5	$196.84	11.196%	$218.8782	$218.88	$218.90	$218.90
Purchase #6	$225.45	3.550%	$233.4535	$233.45	$233.45	$233.50
Purchase #7	$85.64	6.119%	$90.8803	$90.88	$90.90	$90.90
7 purchase totals =	$725.41		$780.7420	$780.74	$780.80	$780.80