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	$94.88	10.648%	$104.9828	$104.98	$105.00	$105.00
Purchase #2	$142.82	13.266%	$161.7665	$161.77	$161.75	$161.80
Purchase #3	$65.56	10.507%	$72.4484	$72.45	$72.45	$72.40
Purchase #4	$170.43	8.331%	$184.6285	$184.63	$184.65	$184.60
Purchase #5	$158.38	12.741%	$178.5592	$178.56	$178.55	$178.60
Purchase #6	$205.51	3.805%	$213.3297	$213.33	$213.35	$213.30
Purchase #7	$127.73	12.621%	$143.8508	$143.85	$143.85	$143.90
7 purchase totals =	$965.31		$1,059.5659	$1,059.57	$1,059.60	$1,059.60