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	$168.73	8.688%	$183.3893	$183.39	$183.40	$183.40
Purchase #2	$87.78	5.507%	$92.614	$92.61	$92.60	$92.60
Purchase #3	$101.62	8.179%	$109.9315	$109.93	$109.95	$109.90
Purchase #4	$131.91	10.208%	$145.3754	$145.38	$145.40	$145.40
Purchase #5	$180.40	13.302%	$204.3968	$204.40	$204.40	$204.40
Purchase #6	$232.73	9.695%	$255.2932	$255.29	$255.30	$255.30
Purchase #7	$182.89	11.793%	$204.4582	$204.46	$204.45	$204.50
7 purchase totals =	$1,086.06		$1,195.4584	$1,195.46	$1,195.50	$1,195.50