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	$55.99	6.414%	$59.5812	$59.58	$59.60	$59.60
Purchase #2	$72.40	7.654%	$77.9415	$77.94	$77.95	$77.90
Purchase #3	$224.96	7.162%	$241.0716	$241.07	$241.05	$241.10
Purchase #4	$215.64	10.392%	$238.0493	$238.05	$238.05	$238.00
Purchase #5	$130.85	6.481%	$139.3304	$139.33	$139.35	$139.30
Purchase #6	$165.88	7.789%	$178.8004	$178.80	$178.80	$178.80
Purchase #7	$239.88	8.208%	$259.5694	$259.57	$259.55	$259.60
7 purchase totals =	$1,105.60		$1,194.3438	$1,194.34	$1,194.35	$1,194.30