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	$68.55	4.134%	$71.3839	$71.38	$71.40	$71.40
Purchase #2	$96.87	3.240%	$100.0086	$100.01	$100.00	$100.00
Purchase #3	$44.61	13.825%	$50.7773	$50.78	$50.80	$50.80
Purchase #4	$165.78	12.720%	$186.8672	$186.87	$186.85	$186.90
Purchase #5	$131.77	7.681%	$141.8913	$141.89	$141.90	$141.90
Purchase #6	$225.31	9.764%	$247.3093	$247.31	$247.30	$247.30
Purchase #7	$248.92	6.491%	$265.0774	$265.08	$265.10	$265.10
7 purchase totals =	$981.81		$1,063.3150	$1,063.32	$1,063.35	$1,063.40