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	$248.54	4.816%	$260.5097	$260.51	$260.50	$260.50
Purchase #2	$173.46	3.249%	$179.0957	$179.10	$179.10	$179.10
Purchase #3	$166.42	7.333%	$178.6236	$178.62	$178.60	$178.60
Purchase #4	$71.57	7.284%	$76.7832	$76.78	$76.80	$76.80
Purchase #5	$121.28	13.723%	$137.9233	$137.92	$137.90	$137.90
Purchase #6	$69.42	4.701%	$72.6834	$72.68	$72.70	$72.70
Purchase #7	$133.33	10.662%	$147.5456	$147.55	$147.55	$147.50
7 purchase totals =	$984.02		$1,053.1645	$1,053.16	$1,053.15	$1,053.10