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	$180.47	5.521%	$190.4337	$190.43	$190.45	$190.40
Purchase #2	$72.95	12.194%	$81.8455	$81.85	$81.85	$81.80
Purchase #3	$244.30	13.837%	$278.1038	$278.10	$278.10	$278.10
Purchase #4	$215.90	3.182%	$222.7699	$222.77	$222.75	$222.80
Purchase #5	$97.95	5.716%	$103.5488	$103.55	$103.55	$103.50
Purchase #6	$171.26	6.781%	$182.8731	$182.87	$182.85	$182.90
Purchase #7	$64.86	10.700%	$71.8	$71.80	$71.80	$71.80
7 purchase totals =	$1,047.69		$1,131.3748	$1,131.37	$1,131.35	$1,131.30