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	$154.64	11.138%	$171.8638	$171.86	$171.85	$171.90
Purchase #2	$146.96	6.550%	$156.5859	$156.59	$156.60	$156.60
Purchase #3	$193.82	13.768%	$220.5051	$220.51	$220.50	$220.50
Purchase #4	$186.64	12.228%	$209.4623	$209.46	$209.45	$209.50
Purchase #5	$228.38	3.343%	$236.0147	$236.01	$236.00	$236.00
Purchase #6	$58.69	8.286%	$63.5531	$63.55	$63.55	$63.60
Purchase #7	$43.57	7.589%	$46.8765	$46.88	$46.90	$46.90
7 purchase totals =	$1,012.70		$1,104.8614	$1,104.86	$1,104.85	$1,105.00