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	$139.69	6.347%	$148.5561	$148.56	$148.55	$148.60
Purchase #2	$89.81	10.156%	$98.9311	$98.93	$98.95	$98.90
Purchase #3	$141.51	10.250%	$156.0148	$156.01	$156.00	$156.00
Purchase #4	$203.34	12.310%	$228.3712	$228.37	$228.35	$228.40
Purchase #5	$128.80	3.146%	$132.852	$132.85	$132.85	$132.90
Purchase #6	$199.38	10.791%	$220.8951	$220.90	$220.90	$220.90
Purchase #7	$140.33	12.838%	$158.3456	$158.35	$158.35	$158.30
7 purchase totals =	$1,042.86		$1,143.9659	$1,143.97	$1,143.95	$1,144.00