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	$245.89	9.668%	$269.6626	$269.66	$269.65	$269.70
Purchase #2	$55.94	11.238%	$62.2265	$62.23	$62.25	$62.20
Purchase #3	$104.59	9.300%	$114.3169	$114.32	$114.30	$114.30
Purchase #4	$94.79	11.299%	$105.5003	$105.50	$105.50	$105.50
Purchase #5	$225.37	13.250%	$255.2315	$255.23	$255.25	$255.20
Purchase #6	$16.54	11.750%	$18.4835	$18.48	$18.50	$18.50
Purchase #7	$6.32	5.451%	$6.6645	$6.66	$6.65	$6.70
7 purchase totals =	$749.44		$832.0858	$832.08	$832.10	$832.10