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	$187.29	5.239%	$197.1021	$197.10	$197.10	$197.10
Purchase #2	$178.42	6.466%	$189.9566	$189.96	$189.95	$190.00
Purchase #3	$154.35	8.803%	$167.9374	$167.94	$167.95	$167.90
Purchase #4	$142.48	6.394%	$151.5902	$151.59	$151.60	$151.60
Purchase #5	$58.32	11.546%	$65.0536	$65.05	$65.05	$65.10
Purchase #6	$82.35	9.143%	$89.8793	$89.88	$89.90	$89.90
Purchase #7	$140.50	5.371%	$148.0463	$148.05	$148.05	$148.00
7 purchase totals =	$943.71		$1,009.5655	$1,009.57	$1,009.60	$1,009.60