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	$71.40	10.587%	$78.9591	$78.96	$78.95	$79.00
Purchase #2	$149.87	13.363%	$169.8971	$169.90	$169.90	$169.90
Purchase #3	$12.48	3.821%	$12.9569	$12.96	$12.95	$13.00
Purchase #4	$245.29	7.353%	$263.3262	$263.33	$263.35	$263.30
Purchase #5	$17.37	5.493%	$18.3241	$18.32	$18.30	$18.30
Purchase #6	$101.80	10.655%	$112.6468	$112.65	$112.65	$112.60
Purchase #7	$198.94	11.834%	$222.4826	$222.48	$222.50	$222.50
7 purchase totals =	$797.15		$878.5928	$878.60	$878.60	$878.60