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	$174.35	12.605%	$196.3268	$196.33	$196.35	$196.30
Purchase #2	$69.91	3.387%	$72.2779	$72.28	$72.30	$72.30
Purchase #3	$220.98	8.688%	$240.1787	$240.18	$240.20	$240.20
Purchase #4	$34.63	13.757%	$39.394	$39.39	$39.40	$39.40
Purchase #5	$164.69	4.373%	$171.8919	$171.89	$171.90	$171.90
Purchase #6	$158.94	13.214%	$179.9423	$179.94	$179.95	$179.90
Purchase #7	$240.43	5.741%	$254.2331	$254.23	$254.25	$254.20
7 purchase totals =	$1,063.93		$1,154.2447	$1,154.24	$1,154.35	$1,154.20