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	$97.39	12.184%	$109.256	$109.26	$109.25	$109.30
Purchase #2	$54.84	9.284%	$59.9313	$59.93	$59.95	$59.90
Purchase #3	$94.83	10.706%	$104.9825	$104.98	$105.00	$105.00
Purchase #4	$157.46	5.167%	$165.596	$165.60	$165.60	$165.60
Purchase #5	$17.97	6.661%	$19.167	$19.17	$19.15	$19.20
Purchase #6	$172.56	9.871%	$189.5934	$189.59	$189.60	$189.60
Purchase #7	$158.79	7.159%	$170.1578	$170.16	$170.15	$170.20
7 purchase totals =	$753.84		$818.6840	$818.69	$818.70	$818.80