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	$69.82	3.681%	$72.3901	$72.39	$72.40	$72.40
Purchase #2	$202.70	10.649%	$224.2855	$224.29	$224.30	$224.30
Purchase #3	$73.83	3.331%	$76.2893	$76.29	$76.30	$76.30
Purchase #4	$88.52	5.723%	$93.586	$93.59	$93.60	$93.60
Purchase #5	$192.78	6.308%	$204.9406	$204.94	$204.95	$204.90
Purchase #6	$198.46	5.121%	$208.6231	$208.62	$208.60	$208.60
Purchase #7	$243.72	12.873%	$275.0941	$275.09	$275.10	$275.10
7 purchase totals =	$1,069.83		$1,155.2087	$1,155.21	$1,155.25	$1,155.20