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	$203.98	4.861%	$213.8955	$213.90	$213.90	$213.90
Purchase #2	$216.27	11.213%	$240.5204	$240.52	$240.50	$240.50
Purchase #3	$162.58	11.141%	$180.693	$180.69	$180.70	$180.70
Purchase #4	$48.47	6.652%	$51.6942	$51.69	$51.70	$51.70
Purchase #5	$9.58	5.347%	$10.0922	$10.09	$10.10	$10.10
Purchase #6	$92.94	3.819%	$96.4894	$96.49	$96.50	$96.50
Purchase #7	$213.70	4.484%	$223.2823	$223.28	$223.30	$223.30
7 purchase totals =	$947.52		$1,016.6670	$1,016.66	$1,016.70	$1,016.70