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	$81.77	3.412%	$84.56	$84.56	$84.55	$84.60
Purchase #2	$30.48	6.661%	$32.5103	$32.51	$32.50	$32.50
Purchase #3	$191.35	10.561%	$211.5585	$211.56	$211.55	$211.60
Purchase #4	$91.94	5.370%	$96.8772	$96.88	$96.90	$96.90
Purchase #5	$76.32	9.451%	$83.533	$83.53	$83.55	$83.50
Purchase #6	$248.86	7.105%	$266.5415	$266.54	$266.55	$266.50
Purchase #7	$82.73	10.614%	$91.511	$91.51	$91.50	$91.50
7 purchase totals =	$803.45		$867.0915	$867.09	$867.10	$867.10