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	$141.59	10.551%	$156.5292	$156.53	$156.55	$156.50
Purchase #2	$235.65	5.131%	$247.7412	$247.74	$247.75	$247.70
Purchase #3	$164.51	4.446%	$171.8241	$171.82	$171.80	$171.80
Purchase #4	$247.47	7.660%	$266.4262	$266.43	$266.45	$266.40
Purchase #5	$33.77	5.863%	$35.7499	$35.75	$35.75	$35.70
Purchase #6	$78.78	9.273%	$86.0853	$86.09	$86.10	$86.10
Purchase #7	$164.74	9.597%	$180.5501	$180.55	$180.55	$180.60
7 purchase totals =	$1,066.51		$1,144.9060	$1,144.91	$1,144.95	$1,144.80