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	$110.81	12.789%	$124.9815	$124.98	$125.00	$125.00
Purchase #2	$219.69	5.150%	$231.004	$231.00	$231.00	$231.00
Purchase #3	$238.70	3.210%	$246.3623	$246.36	$246.35	$246.40
Purchase #4	$41.75	4.458%	$43.6112	$43.61	$43.60	$43.60
Purchase #5	$136.30	8.872%	$148.3925	$148.39	$148.40	$148.40
Purchase #6	$64.69	11.806%	$72.3273	$72.33	$72.35	$72.30
Purchase #7	$153.67	6.829%	$164.1641	$164.16	$164.15	$164.20
7 purchase totals =	$965.61		$1,030.8429	$1,030.83	$1,030.85	$1,030.90