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	$59.35	3.581%	$61.4753	$61.48	$61.50	$61.50
Purchase #2	$62.95	7.759%	$67.8343	$67.83	$67.85	$67.80
Purchase #3	$73.51	10.408%	$81.1609	$81.16	$81.15	$81.20
Purchase #4	$48.46	5.535%	$51.1423	$51.14	$51.15	$51.10
Purchase #5	$22.83	4.673%	$23.8968	$23.90	$23.90	$23.90
Purchase #6	$176.40	11.252%	$196.2485	$196.25	$196.25	$196.20
Purchase #7	$86.93	6.484%	$92.5665	$92.57	$92.55	$92.60
7 purchase totals =	$530.43		$574.3246	$574.33	$574.35	$574.30