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	$79.32	11.350%	$88.3228	$88.32	$88.30	$88.30
Purchase #2	$25.28	10.504%	$27.9354	$27.94	$27.95	$27.90
Purchase #3	$211.81	13.552%	$240.5145	$240.51	$240.50	$240.50
Purchase #4	$186.29	5.599%	$196.7204	$196.72	$196.70	$196.70
Purchase #5	$150.81	10.315%	$166.3661	$166.37	$166.35	$166.40
Purchase #6	$182.26	4.524%	$190.5054	$190.51	$190.50	$190.50
Purchase #7	$15.45	8.221%	$16.7201	$16.72	$16.70	$16.70
7 purchase totals =	$851.22		$927.0847	$927.09	$927.00	$927.00