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	$105.52	11.686%	$117.8511	$117.85	$117.85	$117.90
Purchase #2	$200.47	9.624%	$219.7632	$219.76	$219.75	$219.80
Purchase #3	$117.58	11.679%	$131.3122	$131.31	$131.30	$131.30
Purchase #4	$141.32	6.721%	$150.8181	$150.82	$150.80	$150.80
Purchase #5	$146.71	8.150%	$158.6669	$158.67	$158.65	$158.70
Purchase #6	$129.63	5.314%	$136.5185	$136.52	$136.50	$136.50
Purchase #7	$157.46	12.704%	$177.4637	$177.46	$177.45	$177.50
7 purchase totals =	$998.69		$1,092.3937	$1,092.39	$1,092.30	$1,092.50