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	$29.78	12.353%	$33.4587	$33.46	$33.45	$33.50
Purchase #2	$185.54	7.577%	$199.5984	$199.60	$199.60	$199.60
Purchase #3	$6.25	4.123%	$6.5077	$6.51	$6.50	$6.50
Purchase #4	$250.32	11.227%	$278.4234	$278.42	$278.40	$278.40
Purchase #5	$174.64	9.761%	$191.6866	$191.69	$191.70	$191.70
Purchase #6	$227.88	6.276%	$242.1817	$242.18	$242.20	$242.20
Purchase #7	$92.94	11.453%	$103.5844	$103.58	$103.60	$103.60
7 purchase totals =	$967.35		$1,055.4409	$1,055.44	$1,055.45	$1,055.50