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	$248.96	6.601%	$265.3938	$265.39	$265.40	$265.40
Purchase #2	$73.38	7.508%	$78.8894	$78.89	$78.90	$78.90
Purchase #3	$119.40	8.838%	$129.9526	$129.95	$129.95	$130.00
Purchase #4	$104.61	6.497%	$111.4065	$111.41	$111.40	$111.40
Purchase #5	$240.85	13.532%	$273.4418	$273.44	$273.45	$273.40
Purchase #6	$227.36	7.843%	$245.1918	$245.19	$245.20	$245.20
Purchase #7	$25.67	13.208%	$29.0605	$29.06	$29.05	$29.10
7 purchase totals =	$1,040.23		$1,133.3364	$1,133.33	$1,133.35	$1,133.40