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	$240.61	9.513%	$263.4992	$263.50	$263.50	$263.50
Purchase #2	$242.38	11.733%	$270.8184	$270.82	$270.80	$270.80
Purchase #3	$49.63	9.426%	$54.3081	$54.31	$54.30	$54.30
Purchase #4	$61.57	8.141%	$66.5824	$66.58	$66.60	$66.60
Purchase #5	$161.41	6.267%	$171.5256	$171.53	$171.55	$171.50
Purchase #6	$25.38	3.480%	$26.2632	$26.26	$26.25	$26.30
Purchase #7	$160.52	3.727%	$166.5026	$166.50	$166.50	$166.50
7 purchase totals =	$941.50		$1,019.4995	$1,019.50	$1,019.50	$1,019.50