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	$245.86	9.468%	$269.138	$269.14	$269.15	$269.10
Purchase #2	$97.86	12.334%	$109.9301	$109.93	$109.95	$109.90
Purchase #3	$59.88	4.167%	$62.3752	$62.38	$62.40	$62.40
Purchase #4	$222.54	12.614%	$250.6112	$250.61	$250.60	$250.60
Purchase #5	$226.35	13.340%	$256.5451	$256.55	$256.55	$256.50
Purchase #6	$43.30	4.867%	$45.4074	$45.41	$45.40	$45.40
Purchase #7	$204.41	8.849%	$222.4982	$222.50	$222.50	$222.50
7 purchase totals =	$1,100.20		$1,216.5052	$1,216.52	$1,216.55	$1,216.40