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	$119.94	9.639%	$131.501	$131.50	$131.50	$131.50
Purchase #2	$57.43	11.191%	$63.857	$63.86	$63.85	$63.90
Purchase #3	$93.59	11.234%	$104.1039	$104.10	$104.10	$104.10
Purchase #4	$148.69	5.160%	$156.3624	$156.36	$156.35	$156.40
Purchase #5	$233.84	13.550%	$265.5253	$265.53	$265.55	$265.50
Purchase #6	$153.34	9.850%	$168.444	$168.44	$168.45	$168.40
Purchase #7	$213.44	7.531%	$229.5142	$229.51	$229.50	$229.50
7 purchase totals =	$1,020.27		$1,119.3078	$1,119.30	$1,119.30	$1,119.30