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	$146.72	4.560%	$153.4104	$153.41	$153.40	$153.40
Purchase #2	$41.48	4.813%	$43.4764	$43.48	$43.50	$43.50
Purchase #3	$40.93	4.537%	$42.787	$42.79	$42.80	$42.80
Purchase #4	$177.73	5.552%	$187.5976	$187.60	$187.60	$187.60
Purchase #5	$123.41	6.535%	$131.4748	$131.47	$131.45	$131.50
Purchase #6	$76.86	12.823%	$86.7158	$86.72	$86.70	$86.70
Purchase #7	$225.46	9.142%	$246.0716	$246.07	$246.05	$246.10
7 purchase totals =	$832.59		$891.5336	$891.54	$891.50	$891.60