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	$206.74	4.279%	$215.5864	$215.59	$215.60	$215.60
Purchase #2	$137.76	4.457%	$143.9	$143.90	$143.90	$143.90
Purchase #3	$245.88	6.619%	$262.1548	$262.15	$262.15	$262.20
Purchase #4	$66.67	7.602%	$71.7383	$71.74	$71.75	$71.70
Purchase #5	$152.71	7.779%	$164.5893	$164.59	$164.60	$164.60
Purchase #6	$65.79	8.204%	$71.1874	$71.19	$71.20	$71.20
Purchase #7	$167.53	7.708%	$180.4432	$180.44	$180.45	$180.40
7 purchase totals =	$1,043.08		$1,109.5994	$1,109.60	$1,109.65	$1,109.60