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	$126.63	9.247%	$138.3395	$138.34	$138.35	$138.30
Purchase #2	$185.44	13.340%	$210.1777	$210.18	$210.20	$210.20
Purchase #3	$202.64	8.217%	$219.2909	$219.29	$219.30	$219.30
Purchase #4	$19.76	3.311%	$20.4143	$20.41	$20.40	$20.40
Purchase #5	$71.80	9.423%	$78.5657	$78.57	$78.55	$78.60
Purchase #6	$61.85	6.523%	$65.8845	$65.88	$65.90	$65.90
Purchase #7	$168.47	7.754%	$181.5332	$181.53	$181.55	$181.50
7 purchase totals =	$836.59		$914.2058	$914.20	$914.25	$914.20