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	$194.93	12.125%	$218.5653	$218.57	$218.55	$218.60
Purchase #2	$47.47	3.456%	$49.1106	$49.11	$49.10	$49.10
Purchase #3	$185.93	7.574%	$200.0123	$200.01	$200.00	$200.00
Purchase #4	$248.83	4.295%	$259.5172	$259.52	$259.50	$259.50
Purchase #5	$39.52	11.254%	$43.9676	$43.97	$43.95	$44.00
Purchase #6	$131.95	7.217%	$141.4728	$141.47	$141.45	$141.50
Purchase #7	$140.69	11.115%	$156.3277	$156.33	$156.35	$156.30
7 purchase totals =	$989.32		$1,068.9735	$1,068.98	$1,068.90	$1,069.00