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	$51.31	10.284%	$56.5867	$56.59	$56.60	$56.60
Purchase #2	$109.44	8.674%	$118.9328	$118.93	$118.95	$118.90
Purchase #3	$21.93	12.259%	$24.6184	$24.62	$24.60	$24.60
Purchase #4	$56.61	9.790%	$62.1521	$62.15	$62.15	$62.20
Purchase #5	$139.43	3.483%	$144.2863	$144.29	$144.30	$144.30
Purchase #6	$90.40	4.768%	$94.7103	$94.71	$94.70	$94.70
Purchase #7	$54.32	12.355%	$61.0312	$61.03	$61.05	$61.00
7 purchase totals =	$523.44		$562.3178	$562.32	$562.35	$562.30