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	$172.57	13.629%	$196.0896	$196.09	$196.10	$196.10
Purchase #2	$100.95	13.154%	$114.229	$114.23	$114.25	$114.20
Purchase #3	$166.46	10.757%	$184.3661	$184.37	$184.35	$184.40
Purchase #4	$243.78	11.298%	$271.3223	$271.32	$271.30	$271.30
Purchase #5	$5.59	10.712%	$6.1888	$6.19	$6.20	$6.20
Purchase #6	$60.40	11.582%	$67.3955	$67.40	$67.40	$67.40
Purchase #7	$29.93	7.701%	$32.2349	$32.23	$32.25	$32.20
7 purchase totals =	$779.68		$871.8262	$871.83	$871.85	$871.80