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	$127.49	10.140%	$140.4175	$140.42	$140.40	$140.40
Purchase #2	$90.47	3.788%	$93.897	$93.90	$93.90	$93.90
Purchase #3	$131.43	4.559%	$137.4219	$137.42	$137.40	$137.40
Purchase #4	$155.95	7.315%	$167.3577	$167.36	$167.35	$167.40
Purchase #5	$173.82	3.515%	$179.9298	$179.93	$179.95	$179.90
Purchase #6	$122.76	11.179%	$136.4833	$136.48	$136.50	$136.50
Purchase #7	$196.94	3.803%	$204.4296	$204.43	$204.45	$204.40
7 purchase totals =	$998.86		$1,059.9368	$1,059.94	$1,059.95	$1,059.90