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	$226.64	13.648%	$257.5718	$257.57	$257.55	$257.60
Purchase #2	$126.59	12.530%	$142.4517	$142.45	$142.45	$142.50
Purchase #3	$85.62	4.644%	$89.5962	$89.60	$89.60	$89.60
Purchase #4	$126.43	6.102%	$134.1448	$134.14	$134.15	$134.10
Purchase #5	$138.55	6.190%	$147.1262	$147.13	$147.15	$147.10
Purchase #6	$40.71	12.770%	$45.9087	$45.91	$45.90	$45.90
Purchase #7	$193.47	8.321%	$209.5686	$209.57	$209.55	$209.60
7 purchase totals =	$938.01		$1,026.3680	$1,026.37	$1,026.35	$1,026.40