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	$43.62	3.467%	$45.1323	$45.13	$45.15	$45.10
Purchase #2	$72.27	13.734%	$82.1956	$82.20	$82.20	$82.20
Purchase #3	$59.44	13.249%	$67.3152	$67.32	$67.30	$67.30
Purchase #4	$186.44	5.620%	$196.9179	$196.92	$196.90	$196.90
Purchase #5	$200.85	10.298%	$221.5335	$221.53	$221.55	$221.50
Purchase #6	$22.34	7.803%	$24.0832	$24.08	$24.10	$24.10
Purchase #7	$21.55	11.572%	$24.0438	$24.04	$24.05	$24.00
7 purchase totals =	$606.51		$661.2215	$661.22	$661.25	$661.10