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	$107.86	7.781%	$116.2526	$116.25	$116.25	$116.30
Purchase #2	$74.89	10.541%	$82.7842	$82.78	$82.80	$82.80
Purchase #3	$150.91	6.196%	$160.2604	$160.26	$160.25	$160.30
Purchase #4	$112.50	7.201%	$120.6011	$120.60	$120.60	$120.60
Purchase #5	$220.83	5.172%	$232.2513	$232.25	$232.25	$232.30
Purchase #6	$208.62	10.870%	$231.297	$231.30	$231.30	$231.30
Purchase #7	$192.93	13.525%	$219.0238	$219.02	$219.00	$219.00
7 purchase totals =	$1,068.54		$1,162.4704	$1,162.46	$1,162.45	$1,162.60