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	$139.87	10.845%	$155.0389	$155.04	$155.05	$155.00
Purchase #2	$191.92	13.272%	$217.3916	$217.39	$217.40	$217.40
Purchase #3	$55.88	3.678%	$57.9353	$57.94	$57.95	$57.90
Purchase #4	$222.92	12.799%	$251.4515	$251.45	$251.45	$251.50
Purchase #5	$224.44	11.605%	$250.4863	$250.49	$250.50	$250.50
Purchase #6	$171.88	4.404%	$179.4496	$179.45	$179.45	$179.40
Purchase #7	$30.46	7.257%	$32.6705	$32.67	$32.65	$32.70
7 purchase totals =	$1,037.37		$1,144.4237	$1,144.43	$1,144.45	$1,144.40