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	$38.30	10.249%	$42.2254	$42.23	$42.25	$42.20
Purchase #2	$81.31	6.197%	$86.3488	$86.35	$86.35	$86.30
Purchase #3	$167.30	7.375%	$179.6384	$179.64	$179.65	$179.60
Purchase #4	$32.71	8.277%	$35.4174	$35.42	$35.40	$35.40
Purchase #5	$160.77	9.687%	$176.3438	$176.34	$176.35	$176.30
Purchase #6	$211.38	12.856%	$238.555	$238.56	$238.55	$238.60
Purchase #7	$177.56	10.254%	$195.767	$195.77	$195.75	$195.80
7 purchase totals =	$869.33		$954.2958	$954.31	$954.30	$954.20