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	$108.47	4.603%	$113.4629	$113.46	$113.45	$113.50
Purchase #2	$179.32	9.480%	$196.3195	$196.32	$196.30	$196.30
Purchase #3	$241.71	3.465%	$250.0853	$250.09	$250.10	$250.10
Purchase #4	$126.67	8.417%	$137.3318	$137.33	$137.35	$137.30
Purchase #5	$55.67	3.625%	$57.688	$57.69	$57.70	$57.70
Purchase #6	$62.69	8.360%	$67.9309	$67.93	$67.95	$67.90
Purchase #7	$69.71	13.402%	$79.0525	$79.05	$79.05	$79.10
7 purchase totals =	$844.24		$901.8709	$901.87	$901.90	$901.90