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	$214.71	6.871%	$229.4627	$229.46	$229.45	$229.50
Purchase #2	$79.73	13.190%	$90.2464	$90.25	$90.25	$90.20
Purchase #3	$106.31	12.795%	$119.9124	$119.91	$119.90	$119.90
Purchase #4	$213.25	13.274%	$241.5568	$241.56	$241.55	$241.60
Purchase #5	$61.71	3.443%	$63.8347	$63.83	$63.85	$63.80
Purchase #6	$20.96	6.134%	$22.2457	$22.25	$22.25	$22.20
Purchase #7	$45.44	3.568%	$47.0613	$47.06	$47.05	$47.10
7 purchase totals =	$742.11		$814.3200	$814.32	$814.30	$814.30