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	$51.36	11.508%	$57.2705	$57.27	$57.25	$57.30
Purchase #2	$117.44	11.593%	$131.0548	$131.05	$131.05	$131.10
Purchase #3	$234.97	7.177%	$251.8338	$251.83	$251.85	$251.80
Purchase #4	$91.74	9.256%	$100.2315	$100.23	$100.25	$100.20
Purchase #5	$240.43	10.155%	$264.8457	$264.85	$264.85	$264.80
Purchase #6	$102.89	6.169%	$109.2373	$109.24	$109.25	$109.20
Purchase #7	$138.54	11.164%	$154.0066	$154.01	$154.00	$154.00
7 purchase totals =	$977.37		$1,068.4802	$1,068.48	$1,068.50	$1,068.40