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	$171.75	11.565%	$191.6129	$191.61	$191.60	$191.60
Purchase #2	$136.43	4.576%	$142.673	$142.67	$142.65	$142.70
Purchase #3	$31.55	7.602%	$33.9484	$33.95	$33.95	$33.90
Purchase #4	$183.71	7.544%	$197.5691	$197.57	$197.55	$197.60
Purchase #5	$102.40	9.281%	$111.9037	$111.90	$111.90	$111.90
Purchase #6	$221.79	12.547%	$249.618	$249.62	$249.60	$249.60
Purchase #7	$168.78	13.178%	$191.0218	$191.02	$191.00	$191.00
7 purchase totals =	$1,016.41		$1,118.3469	$1,118.34	$1,118.25	$1,118.30