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	$247.75	13.775%	$281.8776	$281.88	$281.90	$281.90
Purchase #2	$247.78	8.736%	$269.4261	$269.43	$269.45	$269.40
Purchase #3	$84.99	5.231%	$89.4358	$89.44	$89.45	$89.40
Purchase #4	$141.44	7.332%	$151.8104	$151.81	$151.80	$151.80
Purchase #5	$11.86	9.812%	$13.0237	$13.02	$13.00	$13.00
Purchase #6	$36.71	9.618%	$40.2408	$40.24	$40.25	$40.20
Purchase #7	$16.52	11.780%	$18.4661	$18.47	$18.45	$18.50
7 purchase totals =	$787.05		$864.2805	$864.29	$864.30	$864.20