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	$164.46	12.320%	$184.7215	$184.72	$184.70	$184.70
Purchase #2	$239.71	13.853%	$272.917	$272.92	$272.90	$272.90
Purchase #3	$78.67	13.555%	$89.3337	$89.33	$89.35	$89.30
Purchase #4	$123.65	8.270%	$133.8759	$133.88	$133.90	$133.90
Purchase #5	$202.50	8.118%	$218.939	$218.94	$218.95	$218.90
Purchase #6	$195.87	5.434%	$206.5136	$206.51	$206.50	$206.50
Purchase #7	$73.43	12.641%	$82.7123	$82.71	$82.70	$82.70
7 purchase totals =	$1,078.29		$1,189.0130	$1,189.01	$1,189.00	$1,188.90