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	$189.77	8.806%	$206.4811	$206.48	$206.50	$206.50
Purchase #2	$175.66	9.567%	$192.4654	$192.47	$192.45	$192.50
Purchase #3	$176.98	4.856%	$185.5741	$185.57	$185.55	$185.60
Purchase #4	$131.50	7.854%	$141.828	$141.83	$141.85	$141.80
Purchase #5	$179.63	10.727%	$198.8989	$198.90	$198.90	$198.90
Purchase #6	$184.53	13.533%	$209.5024	$209.50	$209.50	$209.50
Purchase #7	$178.79	9.642%	$196.0289	$196.03	$196.05	$196.00
7 purchase totals =	$1,216.86		$1,330.7788	$1,330.78	$1,330.80	$1,330.80