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	$139.91	13.426%	$158.6943	$158.69	$158.70	$158.70
Purchase #2	$205.71	7.584%	$221.311	$221.31	$221.30	$221.30
Purchase #3	$131.82	11.215%	$146.6036	$146.60	$146.60	$146.60
Purchase #4	$94.72	12.837%	$106.8792	$106.88	$106.90	$106.90
Purchase #5	$231.51	12.768%	$261.0692	$261.07	$261.05	$261.10
Purchase #6	$130.79	6.330%	$139.069	$139.07	$139.05	$139.10
Purchase #7	$213.56	5.739%	$225.8162	$225.82	$225.80	$225.80
7 purchase totals =	$1,148.02		$1,259.4425	$1,259.44	$1,259.40	$1,259.50