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	$226.25	6.363%	$240.6463	$240.65	$240.65	$240.60
Purchase #2	$62.84	7.719%	$67.6906	$67.69	$67.70	$67.70
Purchase #3	$57.38	3.500%	$59.3883	$59.39	$59.40	$59.40
Purchase #4	$145.78	9.703%	$159.925	$159.93	$159.95	$159.90
Purchase #5	$237.96	10.775%	$263.6002	$263.60	$263.60	$263.60
Purchase #6	$27.81	8.410%	$30.1488	$30.15	$30.15	$30.10
Purchase #7	$233.30	13.711%	$265.2878	$265.29	$265.30	$265.30
7 purchase totals =	$991.32		$1,086.6870	$1,086.70	$1,086.75	$1,086.60