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	$115.97	13.406%	$131.5169	$131.52	$131.50	$131.50
Purchase #2	$26.43	7.610%	$28.4413	$28.44	$28.45	$28.40
Purchase #3	$163.60	7.600%	$176.0336	$176.03	$176.05	$176.00
Purchase #4	$248.31	10.721%	$274.9313	$274.93	$274.95	$274.90
Purchase #5	$98.26	13.386%	$111.4131	$111.41	$111.40	$111.40
Purchase #6	$155.42	4.565%	$162.5149	$162.51	$162.50	$162.50
Purchase #7	$128.27	10.700%	$141.9949	$141.99	$142.00	$142.00
7 purchase totals =	$936.26		$1,026.8460	$1,026.83	$1,026.85	$1,026.70