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	$69.56	12.545%	$78.2863	$78.29	$78.30	$78.30
Purchase #2	$174.34	11.687%	$194.7151	$194.72	$194.70	$194.70
Purchase #3	$213.56	5.552%	$225.4169	$225.42	$225.40	$225.40
Purchase #4	$106.81	4.532%	$111.6506	$111.65	$111.65	$111.70
Purchase #5	$201.74	7.517%	$216.9048	$216.90	$216.90	$216.90
Purchase #6	$200.36	4.770%	$209.9172	$209.92	$209.90	$209.90
Purchase #7	$13.25	8.833%	$14.4204	$14.42	$14.40	$14.40
7 purchase totals =	$979.62		$1,051.3113	$1,051.32	$1,051.25	$1,051.30