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	$143.62	11.723%	$160.4566	$160.46	$160.45	$160.50
Purchase #2	$96.91	12.630%	$109.1497	$109.15	$109.15	$109.10
Purchase #3	$216.78	4.535%	$226.611	$226.61	$226.60	$226.60
Purchase #4	$131.91	6.437%	$140.401	$140.40	$140.40	$140.40
Purchase #5	$35.81	12.281%	$40.2078	$40.21	$40.20	$40.20
Purchase #6	$41.95	11.414%	$46.7382	$46.74	$46.75	$46.70
Purchase #7	$41.57	3.773%	$43.1384	$43.14	$43.15	$43.10
7 purchase totals =	$708.55		$766.7027	$766.71	$766.70	$766.60