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	$116.91	8.767%	$127.1595	$127.16	$127.15	$127.20
Purchase #2	$208.72	7.264%	$223.8814	$223.88	$223.90	$223.90
Purchase #3	$37.35	3.489%	$38.6531	$38.65	$38.65	$38.70
Purchase #4	$167.45	7.474%	$179.9652	$179.97	$179.95	$180.00
Purchase #5	$132.69	7.373%	$142.4732	$142.47	$142.45	$142.50
Purchase #6	$77.41	12.569%	$87.1397	$87.14	$87.15	$87.10
Purchase #7	$207.34	13.119%	$234.5409	$234.54	$234.55	$234.50
7 purchase totals =	$947.87		$1,033.8130	$1,033.81	$1,033.80	$1,033.90