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	$41.42	10.515%	$45.7753	$45.78	$45.80	$45.80
Purchase #2	$211.31	11.433%	$235.4691	$235.47	$235.45	$235.50
Purchase #3	$86.49	7.681%	$93.1333	$93.13	$93.15	$93.10
Purchase #4	$31.86	6.502%	$33.9315	$33.93	$33.95	$33.90
Purchase #5	$246.35	13.239%	$278.9643	$278.96	$278.95	$279.00
Purchase #6	$164.75	13.447%	$186.9039	$186.90	$186.90	$186.90
Purchase #7	$158.41	6.289%	$168.3724	$168.37	$168.35	$168.40
7 purchase totals =	$940.59		$1,042.5498	$1,042.54	$1,042.55	$1,042.60