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	$159.84	7.490%	$171.812	$171.81	$171.80	$171.80
Purchase #2	$248.59	9.619%	$272.5019	$272.50	$272.50	$272.50
Purchase #3	$129.58	11.826%	$144.9041	$144.90	$144.90	$144.90
Purchase #4	$186.25	6.328%	$198.0359	$198.04	$198.05	$198.00
Purchase #5	$85.64	6.645%	$91.3308	$91.33	$91.35	$91.30
Purchase #6	$108.89	11.175%	$121.0585	$121.06	$121.05	$121.10
Purchase #7	$33.45	11.780%	$37.3904	$37.39	$37.40	$37.40
7 purchase totals =	$952.24		$1,037.0336	$1,037.03	$1,037.05	$1,037.00