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	$164.85	12.411%	$185.3095	$185.31	$185.30	$185.30
Purchase #2	$154.56	10.301%	$170.4812	$170.48	$170.50	$170.50
Purchase #3	$183.75	8.193%	$198.8046	$198.80	$198.80	$198.80
Purchase #4	$125.52	4.798%	$131.5424	$131.54	$131.55	$131.50
Purchase #5	$157.73	11.812%	$176.3611	$176.36	$176.35	$176.40
Purchase #6	$99.52	8.704%	$108.1822	$108.18	$108.20	$108.20
Purchase #7	$90.69	4.157%	$94.46	$94.46	$94.45	$94.50
7 purchase totals =	$976.62		$1,065.1410	$1,065.13	$1,065.15	$1,065.20