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	$167.77	6.630%	$178.8932	$178.89	$178.90	$178.90
Purchase #2	$196.41	6.729%	$209.6264	$209.63	$209.65	$209.60
Purchase #3	$72.82	4.500%	$76.0969	$76.10	$76.10	$76.10
Purchase #4	$94.59	4.582%	$98.9241	$98.92	$98.90	$98.90
Purchase #5	$181.56	8.627%	$197.2232	$197.22	$197.20	$197.20
Purchase #6	$78.35	5.313%	$82.5127	$82.51	$82.50	$82.50
Purchase #7	$38.35	8.868%	$41.7509	$41.75	$41.75	$41.80
7 purchase totals =	$829.85		$885.0274	$885.02	$885.00	$885.00