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	$131.61	7.748%	$141.8071	$141.81	$141.80	$141.80
Purchase #2	$245.39	10.702%	$271.6516	$271.65	$271.65	$271.70
Purchase #3	$134.74	6.522%	$143.5277	$143.53	$143.55	$143.50
Purchase #4	$40.53	5.852%	$42.9018	$42.90	$42.90	$42.90
Purchase #5	$209.34	8.147%	$226.3949	$226.39	$226.40	$226.40
Purchase #6	$24.86	4.270%	$25.9215	$25.92	$25.90	$25.90
Purchase #7	$198.38	5.700%	$209.6877	$209.69	$209.70	$209.70
7 purchase totals =	$984.85		$1,061.8923	$1,061.89	$1,061.90	$1,061.90