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	$210.73	9.825%	$231.4342	$231.43	$231.45	$231.40
Purchase #2	$64.67	9.810%	$71.0141	$71.01	$71.00	$71.00
Purchase #3	$81.45	8.161%	$88.0971	$88.10	$88.10	$88.10
Purchase #4	$191.71	4.780%	$200.8737	$200.87	$200.85	$200.90
Purchase #5	$27.80	13.850%	$31.6503	$31.65	$31.65	$31.70
Purchase #6	$34.85	7.499%	$37.4634	$37.46	$37.45	$37.50
Purchase #7	$102.79	12.642%	$115.7847	$115.78	$115.80	$115.80
7 purchase totals =	$714.00		$776.3175	$776.30	$776.30	$776.40