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	$29.42	9.212%	$32.1302	$32.13	$32.15	$32.10
Purchase #2	$112.76	3.667%	$116.8949	$116.89	$116.90	$116.90
Purchase #3	$182.61	9.792%	$200.4912	$200.49	$200.50	$200.50
Purchase #4	$170.69	3.356%	$176.4184	$176.42	$176.40	$176.40
Purchase #5	$161.96	5.799%	$171.3521	$171.35	$171.35	$171.40
Purchase #6	$122.78	12.791%	$138.4848	$138.48	$138.50	$138.50
Purchase #7	$192.42	13.825%	$219.0221	$219.02	$219.00	$219.00
7 purchase totals =	$972.64		$1,054.7937	$1,054.78	$1,054.80	$1,054.80