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	$116.49	6.393%	$123.9372	$123.94	$123.95	$123.90
Purchase #2	$137.74	9.839%	$151.2922	$151.29	$151.30	$151.30
Purchase #3	$226.82	4.361%	$236.7116	$236.71	$236.70	$236.70
Purchase #4	$104.87	8.439%	$113.72	$113.72	$113.70	$113.70
Purchase #5	$138.94	12.733%	$156.6312	$156.63	$156.65	$156.60
Purchase #6	$156.88	6.110%	$166.4654	$166.47	$166.45	$166.50
Purchase #7	$152.59	7.495%	$164.0266	$164.03	$164.05	$164.00
7 purchase totals =	$1,034.33		$1,112.7842	$1,112.79	$1,112.80	$1,112.70