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	$204.94	3.224%	$211.5473	$211.55	$211.55	$211.50
Purchase #2	$111.62	7.313%	$119.7828	$119.78	$119.80	$119.80
Purchase #3	$69.66	4.107%	$72.5209	$72.52	$72.50	$72.50
Purchase #4	$48.80	4.271%	$50.8842	$50.88	$50.90	$50.90
Purchase #5	$213.68	11.571%	$238.4049	$238.40	$238.40	$238.40
Purchase #6	$85.35	4.552%	$89.2351	$89.24	$89.25	$89.20
Purchase #7	$247.75	13.211%	$280.4803	$280.48	$280.50	$280.50
7 purchase totals =	$981.80		$1,062.8555	$1,062.85	$1,062.90	$1,062.80