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	$246.49	7.727%	$265.5363	$265.54	$265.55	$265.50
Purchase #2	$162.64	7.267%	$174.459	$174.46	$174.45	$174.50
Purchase #3	$248.44	10.610%	$274.7995	$274.80	$274.80	$274.80
Purchase #4	$55.67	5.682%	$58.8332	$58.83	$58.85	$58.80
Purchase #5	$126.48	11.433%	$140.9405	$140.94	$140.95	$140.90
Purchase #6	$83.69	7.469%	$89.9408	$89.94	$89.95	$89.90
Purchase #7	$24.51	5.196%	$25.7835	$25.78	$25.80	$25.80
7 purchase totals =	$947.92		$1,030.2928	$1,030.29	$1,030.35	$1,030.20