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	$156.74	12.681%	$176.6162	$176.62	$176.60	$176.60
Purchase #2	$176.54	6.172%	$187.436	$187.44	$187.45	$187.40
Purchase #3	$57.59	3.469%	$59.5878	$59.59	$59.60	$59.60
Purchase #4	$35.98	11.560%	$40.1393	$40.14	$40.15	$40.10
Purchase #5	$188.99	13.667%	$214.8193	$214.82	$214.80	$214.80
Purchase #6	$20.72	3.149%	$21.3725	$21.37	$21.35	$21.40
Purchase #7	$147.75	13.833%	$168.1883	$168.19	$168.20	$168.20
7 purchase totals =	$784.31		$868.1594	$868.17	$868.15	$868.10