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	$234.63	13.514%	$266.3379	$266.34	$266.35	$266.30
Purchase #2	$248.59	4.204%	$259.0407	$259.04	$259.05	$259.00
Purchase #3	$96.33	3.332%	$99.5397	$99.54	$99.55	$99.50
Purchase #4	$95.56	8.288%	$103.48	$103.48	$103.50	$103.50
Purchase #5	$121.39	7.824%	$130.8876	$130.89	$130.90	$130.90
Purchase #6	$176.43	8.557%	$191.5271	$191.53	$191.55	$191.50
Purchase #7	$143.31	9.252%	$156.569	$156.57	$156.55	$156.60
7 purchase totals =	$1,116.24		$1,207.3820	$1,207.39	$1,207.45	$1,207.30