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	$192.95	10.605%	$213.4123	$213.41	$213.40	$213.40
Purchase #2	$108.61	9.360%	$118.7759	$118.78	$118.80	$118.80
Purchase #3	$96.27	5.576%	$101.638	$101.64	$101.65	$101.60
Purchase #4	$220.79	13.645%	$250.9168	$250.92	$250.90	$250.90
Purchase #5	$19.58	11.778%	$21.8861	$21.89	$21.90	$21.90
Purchase #6	$170.50	5.170%	$179.3149	$179.31	$179.30	$179.30
Purchase #7	$72.94	12.520%	$82.0721	$82.07	$82.05	$82.10
7 purchase totals =	$881.64		$968.0161	$968.02	$968.00	$968.00