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	$214.72	3.320%	$221.8487	$221.85	$221.85	$221.80
Purchase #2	$79.91	11.487%	$89.0893	$89.09	$89.10	$89.10
Purchase #3	$246.40	10.480%	$272.2227	$272.22	$272.20	$272.20
Purchase #4	$87.77	12.123%	$98.4104	$98.41	$98.40	$98.40
Purchase #5	$48.43	10.259%	$53.3984	$53.40	$53.40	$53.40
Purchase #6	$144.85	13.831%	$164.8842	$164.88	$164.90	$164.90
Purchase #7	$199.69	9.678%	$219.016	$219.02	$219.00	$219.00
7 purchase totals =	$1,021.77		$1,118.8697	$1,118.87	$1,118.85	$1,118.80