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	$172.78	8.778%	$187.9466	$187.95	$187.95	$187.90
Purchase #2	$104.39	4.296%	$108.8746	$108.87	$108.85	$108.90
Purchase #3	$221.43	5.620%	$233.8744	$233.87	$233.85	$233.90
Purchase #4	$93.55	4.645%	$97.8954	$97.90	$97.90	$97.90
Purchase #5	$69.26	5.214%	$72.8712	$72.87	$72.85	$72.90
Purchase #6	$177.90	12.289%	$199.7621	$199.76	$199.75	$199.80
Purchase #7	$219.77	8.298%	$238.0065	$238.01	$238.00	$238.00
7 purchase totals =	$1,059.08		$1,139.2308	$1,139.23	$1,139.15	$1,139.30