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	$81.38	13.580%	$92.4314	$92.43	$92.45	$92.40
Purchase #2	$183.37	11.212%	$203.9294	$203.93	$203.95	$203.90
Purchase #3	$76.80	12.362%	$86.294	$86.29	$86.30	$86.30
Purchase #4	$175.72	10.624%	$194.3885	$194.39	$194.40	$194.40
Purchase #5	$21.61	11.258%	$24.0429	$24.04	$24.05	$24.00
Purchase #6	$18.34	12.285%	$20.5931	$20.59	$20.60	$20.60
Purchase #7	$65.36	10.639%	$72.3137	$72.31	$72.30	$72.30
7 purchase totals =	$622.58		$693.9930	$693.98	$694.05	$693.90