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	$116.90	9.351%	$127.8313	$127.83	$127.85	$127.80
Purchase #2	$32.30	6.712%	$34.468	$34.47	$34.45	$34.50
Purchase #3	$171.33	12.861%	$193.3648	$193.36	$193.35	$193.40
Purchase #4	$90.71	13.381%	$102.8479	$102.85	$102.85	$102.80
Purchase #5	$215.86	5.421%	$227.5618	$227.56	$227.55	$227.60
Purchase #6	$13.54	5.400%	$14.2712	$14.27	$14.25	$14.30
Purchase #7	$78.30	8.334%	$84.8255	$84.83	$84.85	$84.80
7 purchase totals =	$718.94		$785.1705	$785.17	$785.15	$785.20