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	$136.64	5.869%	$144.6594	$144.66	$144.65	$144.70
Purchase #2	$14.69	3.190%	$15.1586	$15.16	$15.15	$15.20
Purchase #3	$218.89	10.619%	$242.1339	$242.13	$242.15	$242.10
Purchase #4	$203.29	3.292%	$209.9823	$209.98	$210.00	$210.00
Purchase #5	$150.86	11.513%	$168.2285	$168.23	$168.25	$168.20
Purchase #6	$34.35	13.180%	$38.8773	$38.88	$38.90	$38.90
Purchase #7	$213.34	12.655%	$240.3382	$240.34	$240.35	$240.30
7 purchase totals =	$972.06		$1,059.3782	$1,059.38	$1,059.45	$1,059.40