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	$181.37	9.691%	$198.9466	$198.95	$198.95	$198.90
Purchase #2	$149.26	10.494%	$164.9233	$164.92	$164.90	$164.90
Purchase #3	$10.70	8.151%	$11.5722	$11.57	$11.55	$11.60
Purchase #4	$21.42	12.685%	$24.1371	$24.14	$24.15	$24.10
Purchase #5	$181.71	8.198%	$196.6066	$196.61	$196.60	$196.60
Purchase #6	$32.41	11.617%	$36.1751	$36.18	$36.20	$36.20
Purchase #7	$19.54	10.809%	$21.6521	$21.65	$21.65	$21.70
7 purchase totals =	$596.41		$654.0130	$654.02	$654.00	$654.00