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	$161.39	12.511%	$181.5815	$181.58	$181.60	$181.60
Purchase #2	$123.27	11.809%	$137.827	$137.83	$137.85	$137.80
Purchase #3	$157.94	13.476%	$179.224	$179.22	$179.20	$179.20
Purchase #4	$123.33	12.286%	$138.4823	$138.48	$138.50	$138.50
Purchase #5	$80.53	6.320%	$85.6195	$85.62	$85.60	$85.60
Purchase #6	$169.56	13.658%	$192.7185	$192.72	$192.70	$192.70
Purchase #7	$198.39	13.205%	$224.5874	$224.59	$224.60	$224.60
7 purchase totals =	$1,014.41		$1,140.0402	$1,140.04	$1,140.05	$1,140.00