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	$137.86	3.446%	$142.6107	$142.61	$142.60	$142.60
Purchase #2	$231.76	12.263%	$260.1807	$260.18	$260.20	$260.20
Purchase #3	$153.88	8.172%	$166.4551	$166.46	$166.45	$166.50
Purchase #4	$39.26	8.467%	$42.5841	$42.58	$42.60	$42.60
Purchase #5	$182.55	9.142%	$199.2387	$199.24	$199.25	$199.20
Purchase #6	$157.86	9.395%	$172.6909	$172.69	$172.70	$172.70
Purchase #7	$61.40	13.826%	$69.8892	$69.89	$69.90	$69.90
7 purchase totals =	$964.57		$1,053.6494	$1,053.65	$1,053.70	$1,053.70