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	$80.63	7.824%	$86.9385	$86.94	$86.95	$86.90
Purchase #2	$78.64	12.499%	$88.4692	$88.47	$88.45	$88.50
Purchase #3	$110.88	5.264%	$116.7167	$116.72	$116.70	$116.70
Purchase #4	$170.67	12.851%	$192.6028	$192.60	$192.60	$192.60
Purchase #5	$86.62	6.737%	$92.4556	$92.46	$92.45	$92.50
Purchase #6	$38.86	9.470%	$42.54	$42.54	$42.55	$42.50
Purchase #7	$160.60	10.335%	$177.198	$177.20	$177.20	$177.20
7 purchase totals =	$726.90		$796.9208	$796.93	$796.90	$796.90