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	$205.50	7.739%	$221.4036	$221.40	$221.40	$221.40
Purchase #2	$169.32	8.601%	$183.8832	$183.88	$183.90	$183.90
Purchase #3	$9.26	6.143%	$9.8288	$9.83	$9.85	$9.80
Purchase #4	$84.67	12.684%	$95.4095	$95.41	$95.40	$95.40
Purchase #5	$72.81	7.158%	$78.0217	$78.02	$78.00	$78.00
Purchase #6	$101.29	8.103%	$109.4975	$109.50	$109.50	$109.50
Purchase #7	$80.79	10.759%	$89.4822	$89.48	$89.50	$89.50
7 purchase totals =	$723.64		$787.5265	$787.52	$787.55	$787.50