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	$40.42	9.561%	$44.2846	$44.28	$44.30	$44.30
Purchase #2	$77.30	6.471%	$82.3021	$82.30	$82.30	$82.30
Purchase #3	$99.95	9.263%	$109.2084	$109.21	$109.20	$109.20
Purchase #4	$240.27	3.590%	$248.8957	$248.90	$248.90	$248.90
Purchase #5	$216.29	11.463%	$241.0833	$241.08	$241.10	$241.10
Purchase #6	$29.99	11.755%	$33.5153	$33.52	$33.50	$33.50
Purchase #7	$188.29	10.564%	$208.181	$208.18	$208.20	$208.20
7 purchase totals =	$892.51		$967.4704	$967.47	$967.50	$967.50