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	$96.86	6.280%	$102.9428	$102.94	$102.95	$102.90
Purchase #2	$208.86	7.811%	$225.1741	$225.17	$225.15	$225.20
Purchase #3	$160.65	12.215%	$180.2734	$180.27	$180.25	$180.30
Purchase #4	$47.96	3.129%	$49.4607	$49.46	$49.45	$49.50
Purchase #5	$99.29	8.670%	$107.8984	$107.90	$107.90	$107.90
Purchase #6	$194.56	13.258%	$220.3548	$220.35	$220.35	$220.40
Purchase #7	$119.38	3.731%	$123.8341	$123.83	$123.85	$123.80
7 purchase totals =	$927.56		$1,009.9383	$1,009.92	$1,009.90	$1,010.00