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	$88.65	9.756%	$97.2987	$97.30	$97.30	$97.30
Purchase #2	$75.79	8.571%	$82.286	$82.29	$82.30	$82.30
Purchase #3	$174.63	10.474%	$192.9207	$192.92	$192.90	$192.90
Purchase #4	$193.49	7.647%	$208.2862	$208.29	$208.30	$208.30
Purchase #5	$126.42	13.504%	$143.4918	$143.49	$143.50	$143.50
Purchase #6	$40.56	5.599%	$42.831	$42.83	$42.85	$42.80
Purchase #7	$243.79	12.121%	$273.3398	$273.34	$273.35	$273.30
7 purchase totals =	$943.33		$1,040.4542	$1,040.46	$1,040.50	$1,040.40