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	$143.48	5.780%	$151.7731	$151.77	$151.75	$151.80
Purchase #2	$100.95	4.710%	$105.7047	$105.70	$105.70	$105.70
Purchase #3	$155.52	7.123%	$166.5977	$166.60	$166.60	$166.60
Purchase #4	$131.86	4.596%	$137.9203	$137.92	$137.90	$137.90
Purchase #5	$178.61	12.448%	$200.8434	$200.84	$200.85	$200.80
Purchase #6	$136.59	13.858%	$155.5186	$155.52	$155.50	$155.50
Purchase #7	$119.36	11.113%	$132.6245	$132.62	$132.60	$132.60
7 purchase totals =	$966.37		$1,050.9823	$1,050.97	$1,050.90	$1,050.90