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	$241.47	8.855%	$262.8522	$262.85	$262.85	$262.90
Purchase #2	$250.25	7.290%	$268.4932	$268.49	$268.50	$268.50
Purchase #3	$138.41	3.515%	$143.2751	$143.28	$143.30	$143.30
Purchase #4	$131.41	8.611%	$142.7257	$142.73	$142.75	$142.70
Purchase #5	$185.78	3.226%	$191.7733	$191.77	$191.75	$191.80
Purchase #6	$17.90	13.712%	$20.3544	$20.35	$20.35	$20.40
Purchase #7	$66.70	6.510%	$71.0422	$71.04	$71.05	$71.00
7 purchase totals =	$1,031.92		$1,100.5161	$1,100.51	$1,100.55	$1,100.60