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	$98.97	9.716%	$108.5859	$108.59	$108.60	$108.60
Purchase #2	$91.40	10.242%	$100.7612	$100.76	$100.75	$100.80
Purchase #3	$56.35	5.553%	$59.4791	$59.48	$59.50	$59.50
Purchase #4	$164.47	7.340%	$176.5421	$176.54	$176.55	$176.50
Purchase #5	$167.88	10.822%	$186.048	$186.05	$186.05	$186.00
Purchase #6	$100.50	3.510%	$104.0276	$104.03	$104.05	$104.00
Purchase #7	$245.54	11.441%	$273.6322	$273.63	$273.65	$273.60
7 purchase totals =	$925.11		$1,009.0761	$1,009.08	$1,009.15	$1,009.00