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	$238.67	4.704%	$249.897	$249.90	$249.90	$249.90
Purchase #2	$95.94	3.758%	$99.5454	$99.55	$99.55	$99.50
Purchase #3	$179.61	12.496%	$202.0541	$202.05	$202.05	$202.10
Purchase #4	$85.81	13.695%	$97.5617	$97.56	$97.55	$97.60
Purchase #5	$83.54	7.645%	$89.9266	$89.93	$89.95	$89.90
Purchase #6	$211.63	12.620%	$238.3377	$238.34	$238.35	$238.30
Purchase #7	$105.98	13.676%	$120.4738	$120.47	$120.45	$120.50
7 purchase totals =	$1,001.18		$1,097.7963	$1,097.80	$1,097.80	$1,097.80