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	$55.94	5.801%	$59.1851	$59.19	$59.20	$59.20
Purchase #2	$224.46	8.641%	$243.8556	$243.86	$243.85	$243.90
Purchase #3	$14.97	3.105%	$15.4348	$15.43	$15.45	$15.40
Purchase #4	$119.54	3.112%	$123.2601	$123.26	$123.25	$123.30
Purchase #5	$212.52	10.844%	$235.5657	$235.57	$235.55	$235.60
Purchase #6	$167.93	10.193%	$185.0471	$185.05	$185.05	$185.00
Purchase #7	$154.29	12.615%	$173.7537	$173.75	$173.75	$173.80
7 purchase totals =	$949.65		$1,036.1021	$1,036.11	$1,036.10	$1,036.20