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	$75.43	4.331%	$78.6969	$78.70	$78.70	$78.70
Purchase #2	$75.93	9.143%	$82.8723	$82.87	$82.85	$82.90
Purchase #3	$164.49	9.369%	$179.9011	$179.90	$179.90	$179.90
Purchase #4	$237.72	7.555%	$255.6797	$255.68	$255.70	$255.70
Purchase #5	$62.63	8.334%	$67.8496	$67.85	$67.85	$67.80
Purchase #6	$97.51	8.350%	$105.6521	$105.65	$105.65	$105.70
Purchase #7	$151.59	8.726%	$164.8177	$164.82	$164.80	$164.80
7 purchase totals =	$865.30		$935.4694	$935.47	$935.45	$935.50