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	$113.61	11.118%	$126.2412	$126.24	$126.25	$126.20
Purchase #2	$63.41	13.818%	$72.172	$72.17	$72.15	$72.20
Purchase #3	$20.84	5.266%	$21.9374	$21.94	$21.95	$21.90
Purchase #4	$60.58	10.633%	$67.0215	$67.02	$67.00	$67.00
Purchase #5	$241.64	6.185%	$256.5854	$256.59	$256.60	$256.60
Purchase #6	$80.70	10.508%	$89.18	$89.18	$89.20	$89.20
Purchase #7	$173.27	4.584%	$181.2127	$181.21	$181.20	$181.20
7 purchase totals =	$754.05		$814.3502	$814.35	$814.35	$814.30