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	$53.95	11.821%	$60.3274	$60.33	$60.35	$60.30
Purchase #2	$117.52	8.831%	$127.8982	$127.90	$127.90	$127.90
Purchase #3	$163.97	9.426%	$179.4258	$179.43	$179.45	$179.40
Purchase #4	$168.30	6.862%	$179.8487	$179.85	$179.85	$179.80
Purchase #5	$200.40	11.239%	$222.923	$222.92	$222.90	$222.90
Purchase #6	$29.58	9.322%	$32.3374	$32.34	$32.35	$32.30
Purchase #7	$125.66	11.564%	$140.1913	$140.19	$140.20	$140.20
7 purchase totals =	$859.38		$942.9518	$942.96	$943.00	$942.80