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	$71.43	10.240%	$78.7444	$78.74	$78.75	$78.70
Purchase #2	$102.92	9.369%	$112.5626	$112.56	$112.55	$112.60
Purchase #3	$79.96	12.752%	$90.1565	$90.16	$90.15	$90.20
Purchase #4	$235.29	10.239%	$259.3813	$259.38	$259.40	$259.40
Purchase #5	$159.32	4.811%	$166.9849	$166.98	$167.00	$167.00
Purchase #6	$66.86	4.582%	$69.9235	$69.92	$69.90	$69.90
Purchase #7	$39.71	10.627%	$43.93	$43.93	$43.95	$43.90
7 purchase totals =	$755.49		$821.6832	$821.67	$821.70	$821.70