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	$158.38	13.286%	$179.4224	$179.42	$179.40	$179.40
Purchase #2	$153.35	9.444%	$167.8324	$167.83	$167.85	$167.80
Purchase #3	$59.30	13.580%	$67.3529	$67.35	$67.35	$67.40
Purchase #4	$93.38	8.733%	$101.5349	$101.53	$101.55	$101.50
Purchase #5	$170.58	12.212%	$191.4112	$191.41	$191.40	$191.40
Purchase #6	$147.96	9.260%	$161.6611	$161.66	$161.65	$161.70
Purchase #7	$249.37	9.637%	$273.4018	$273.40	$273.40	$273.40
7 purchase totals =	$1,032.32		$1,142.6167	$1,142.60	$1,142.60	$1,142.60