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	$193.64	3.315%	$200.0592	$200.06	$200.05	$200.10
Purchase #2	$94.35	11.124%	$104.8455	$104.85	$104.85	$104.80
Purchase #3	$237.54	10.180%	$261.7216	$261.72	$261.70	$261.70
Purchase #4	$34.39	13.103%	$38.8961	$38.90	$38.90	$38.90
Purchase #5	$58.27	10.505%	$64.3913	$64.39	$64.40	$64.40
Purchase #6	$176.60	13.191%	$199.8953	$199.90	$199.90	$199.90
Purchase #7	$124.57	12.477%	$140.1126	$140.11	$140.10	$140.10
7 purchase totals =	$919.36		$1,009.9216	$1,009.93	$1,009.90	$1,009.90