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	$56.91	5.287%	$59.9188	$59.92	$59.90	$59.90
Purchase #2	$84.96	12.119%	$95.2563	$95.26	$95.25	$95.30
Purchase #3	$224.96	5.684%	$237.7467	$237.75	$237.75	$237.70
Purchase #4	$184.49	5.162%	$194.0134	$194.01	$194.00	$194.00
Purchase #5	$91.43	5.341%	$96.3133	$96.31	$96.30	$96.30
Purchase #6	$196.77	10.223%	$216.8858	$216.89	$216.90	$216.90
Purchase #7	$12.30	13.374%	$13.945	$13.95	$13.95	$13.90
7 purchase totals =	$851.82		$914.0793	$914.09	$914.05	$914.00