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	$163.89	3.473%	$169.5819	$169.58	$169.60	$169.60
Purchase #2	$140.54	3.125%	$144.9319	$144.93	$144.95	$144.90
Purchase #3	$241.52	9.648%	$264.8218	$264.82	$264.80	$264.80
Purchase #4	$43.25	3.301%	$44.6777	$44.68	$44.70	$44.70
Purchase #5	$184.46	3.741%	$191.3606	$191.36	$191.35	$191.40
Purchase #6	$69.73	9.711%	$76.5015	$76.50	$76.50	$76.50
Purchase #7	$150.68	3.455%	$155.886	$155.89	$155.90	$155.90
7 purchase totals =	$994.07		$1,047.7614	$1,047.76	$1,047.80	$1,047.80