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	$55.71	6.676%	$59.4292	$59.43	$59.45	$59.40
Purchase #2	$236.46	12.175%	$265.249	$265.25	$265.25	$265.20
Purchase #3	$198.43	8.669%	$215.6319	$215.63	$215.65	$215.60
Purchase #4	$82.48	8.237%	$89.2739	$89.27	$89.25	$89.30
Purchase #5	$207.31	8.772%	$225.4952	$225.50	$225.50	$225.50
Purchase #6	$176.29	6.586%	$187.9005	$187.90	$187.90	$187.90
Purchase #7	$103.41	5.190%	$108.777	$108.78	$108.80	$108.80
7 purchase totals =	$1,060.09		$1,151.7567	$1,151.76	$1,151.80	$1,151.70