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	$84.45	11.108%	$93.8307	$93.83	$93.85	$93.80
Purchase #2	$189.77	4.759%	$198.8012	$198.80	$198.80	$198.80
Purchase #3	$69.85	12.581%	$78.6378	$78.64	$78.65	$78.60
Purchase #4	$92.82	4.189%	$96.7082	$96.71	$96.70	$96.70
Purchase #5	$70.75	10.573%	$78.2304	$78.23	$78.25	$78.20
Purchase #6	$118.75	12.736%	$133.874	$133.87	$133.85	$133.90
Purchase #7	$128.43	11.113%	$142.7024	$142.70	$142.70	$142.70
7 purchase totals =	$754.82		$822.7847	$822.78	$822.80	$822.70