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	$77.89	5.425%	$82.1155	$82.12	$82.10	$82.10
Purchase #2	$238.25	7.557%	$256.2546	$256.25	$256.25	$256.30
Purchase #3	$210.65	8.641%	$228.8523	$228.85	$228.85	$228.90
Purchase #4	$184.54	4.813%	$193.4219	$193.42	$193.40	$193.40
Purchase #5	$107.38	10.423%	$118.5722	$118.57	$118.55	$118.60
Purchase #6	$92.43	4.522%	$96.6097	$96.61	$96.60	$96.60
Purchase #7	$125.47	10.402%	$138.5214	$138.52	$138.50	$138.50
7 purchase totals =	$1,036.61		$1,114.3476	$1,114.34	$1,114.25	$1,114.40