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	$188.56	13.239%	$213.5235	$213.52	$213.50	$213.50
Purchase #2	$131.60	4.437%	$137.4391	$137.44	$137.45	$137.40
Purchase #3	$89.87	13.768%	$102.2433	$102.24	$102.25	$102.20
Purchase #4	$142.31	7.404%	$152.8466	$152.85	$152.85	$152.80
Purchase #5	$127.71	8.712%	$138.8361	$138.84	$138.85	$138.80
Purchase #6	$218.63	10.152%	$240.8253	$240.83	$240.85	$240.80
Purchase #7	$71.43	7.623%	$76.8751	$76.88	$76.90	$76.90
7 purchase totals =	$970.11		$1,062.5890	$1,062.60	$1,062.65	$1,062.40