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	$160.50	13.609%	$182.3424	$182.34	$182.35	$182.30
Purchase #2	$235.26	12.860%	$265.5144	$265.51	$265.50	$265.50
Purchase #3	$227.62	9.296%	$248.7796	$248.78	$248.80	$248.80
Purchase #4	$59.48	12.660%	$67.0102	$67.01	$67.00	$67.00
Purchase #5	$151.85	10.403%	$167.647	$167.65	$167.65	$167.60
Purchase #6	$57.93	6.455%	$61.6694	$61.67	$61.65	$61.70
Purchase #7	$187.63	5.729%	$198.3793	$198.38	$198.40	$198.40
7 purchase totals =	$1,080.27		$1,191.3423	$1,191.34	$1,191.35	$1,191.30