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	$71.90	9.253%	$78.5529	$78.55	$78.55	$78.60
Purchase #2	$117.94	6.190%	$125.2405	$125.24	$125.25	$125.20
Purchase #3	$51.47	5.775%	$54.4424	$54.44	$54.45	$54.40
Purchase #4	$166.61	4.109%	$173.456	$173.46	$173.45	$173.50
Purchase #5	$162.54	5.497%	$171.4748	$171.47	$171.45	$171.50
Purchase #6	$73.48	13.280%	$83.2381	$83.24	$83.25	$83.20
Purchase #7	$216.80	7.701%	$233.4958	$233.50	$233.50	$233.50
7 purchase totals =	$860.74		$919.9005	$919.90	$919.90	$919.90