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	$188.25	6.509%	$200.5032	$200.50	$200.50	$200.50
Purchase #2	$72.35	7.870%	$78.0439	$78.04	$78.05	$78.00
Purchase #3	$83.86	5.583%	$88.5419	$88.54	$88.55	$88.50
Purchase #4	$202.33	9.579%	$221.7112	$221.71	$221.70	$221.70
Purchase #5	$243.40	4.196%	$253.6131	$253.61	$253.60	$253.60
Purchase #6	$24.85	12.419%	$27.9361	$27.94	$27.95	$27.90
Purchase #7	$125.29	4.696%	$131.1736	$131.17	$131.15	$131.20
7 purchase totals =	$940.33		$1,001.5230	$1,001.51	$1,001.50	$1,001.40