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	$209.37	11.215%	$232.8508	$232.85	$232.85	$232.90
Purchase #2	$76.26	12.707%	$85.9504	$85.95	$85.95	$86.00
Purchase #3	$43.73	7.333%	$46.9367	$46.94	$46.95	$46.90
Purchase #4	$62.26	10.595%	$68.8564	$68.86	$68.85	$68.90
Purchase #5	$86.35	3.146%	$89.0666	$89.07	$89.05	$89.10
Purchase #6	$69.72	3.712%	$72.308	$72.31	$72.30	$72.30
Purchase #7	$67.73	3.752%	$70.2712	$70.27	$70.25	$70.30
7 purchase totals =	$615.42		$666.2401	$666.25	$666.20	$666.40