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	$196.92	11.650%	$219.8612	$219.86	$219.85	$219.90
Purchase #2	$184.59	6.431%	$196.461	$196.46	$196.45	$196.50
Purchase #3	$90.64	7.766%	$97.6791	$97.68	$97.70	$97.70
Purchase #4	$6.81	10.645%	$7.5349	$7.53	$7.55	$7.50
Purchase #5	$139.80	9.485%	$153.06	$153.06	$153.05	$153.10
Purchase #6	$241.76	12.135%	$271.0976	$271.10	$271.10	$271.10
Purchase #7	$44.86	13.273%	$50.8143	$50.81	$50.80	$50.80
7 purchase totals =	$905.38		$996.5081	$996.50	$996.50	$996.60