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	$189.69	10.805%	$210.186	$210.19	$210.20	$210.20
Purchase #2	$67.55	7.291%	$72.4751	$72.48	$72.50	$72.50
Purchase #3	$57.29	3.853%	$59.4974	$59.50	$59.50	$59.50
Purchase #4	$122.45	13.733%	$139.2661	$139.27	$139.25	$139.30
Purchase #5	$125.74	10.547%	$139.0018	$139.00	$139.00	$139.00
Purchase #6	$116.53	3.329%	$120.4093	$120.41	$120.40	$120.40
Purchase #7	$137.83	10.843%	$152.7749	$152.77	$152.75	$152.80
7 purchase totals =	$817.08		$893.6106	$893.62	$893.60	$893.70