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	$91.80	5.118%	$96.4983	$96.50	$96.50	$96.50
Purchase #2	$150.84	7.650%	$162.3793	$162.38	$162.40	$162.40
Purchase #3	$47.31	10.248%	$52.1583	$52.16	$52.15	$52.20
Purchase #4	$225.47	6.228%	$239.5123	$239.51	$239.50	$239.50
Purchase #5	$12.31	3.274%	$12.713	$12.71	$12.70	$12.70
Purchase #6	$176.27	10.532%	$194.8348	$194.83	$194.85	$194.80
Purchase #7	$250.45	12.576%	$281.9466	$281.95	$281.95	$281.90
7 purchase totals =	$954.45		$1,040.0426	$1,040.04	$1,040.05	$1,040.00