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	$135.37	11.299%	$150.6655	$150.67	$150.65	$150.70
Purchase #2	$227.36	5.833%	$240.6219	$240.62	$240.60	$240.60
Purchase #3	$71.42	9.443%	$78.1642	$78.16	$78.15	$78.20
Purchase #4	$213.55	7.353%	$229.2523	$229.25	$229.25	$229.30
Purchase #5	$193.76	3.438%	$200.4215	$200.42	$200.40	$200.40
Purchase #6	$132.75	11.720%	$148.3083	$148.31	$148.30	$148.30
Purchase #7	$175.62	13.821%	$199.8924	$199.89	$199.90	$199.90
7 purchase totals =	$1,149.83		$1,247.3261	$1,247.32	$1,247.25	$1,247.40