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	$94.59	8.463%	$102.5952	$102.60	$102.60	$102.60
Purchase #2	$137.27	13.545%	$155.8632	$155.86	$155.85	$155.90
Purchase #3	$201.65	6.780%	$215.3219	$215.32	$215.30	$215.30
Purchase #4	$92.51	7.632%	$99.5704	$99.57	$99.55	$99.60
Purchase #5	$203.25	9.414%	$222.384	$222.38	$222.40	$222.40
Purchase #6	$208.94	6.686%	$222.9097	$222.91	$222.90	$222.90
Purchase #7	$156.97	8.325%	$170.0378	$170.04	$170.05	$170.00
7 purchase totals =	$1,095.18		$1,188.6822	$1,188.68	$1,188.65	$1,188.70