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	$87.46	4.659%	$91.5348	$91.53	$91.55	$91.50
Purchase #2	$73.32	4.830%	$76.8614	$76.86	$76.85	$76.90
Purchase #3	$116.47	12.869%	$131.4585	$131.46	$131.45	$131.50
Purchase #4	$72.75	8.480%	$78.9192	$78.92	$78.90	$78.90
Purchase #5	$166.94	4.396%	$174.2787	$174.28	$174.30	$174.30
Purchase #6	$19.40	4.217%	$20.2181	$20.22	$20.20	$20.20
Purchase #7	$238.78	7.600%	$256.9273	$256.93	$256.95	$256.90
7 purchase totals =	$775.12		$830.1980	$830.20	$830.20	$830.20