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	$51.94	10.826%	$57.563	$57.56	$57.55	$57.60
Purchase #2	$101.37	3.391%	$104.8075	$104.81	$104.80	$104.80
Purchase #3	$225.94	5.437%	$238.2244	$238.22	$238.20	$238.20
Purchase #4	$214.79	4.185%	$223.779	$223.78	$223.80	$223.80
Purchase #5	$31.67	7.706%	$34.1105	$34.11	$34.10	$34.10
Purchase #6	$29.25	10.524%	$32.3283	$32.33	$32.35	$32.30
Purchase #7	$38.92	8.290%	$42.1465	$42.15	$42.15	$42.10
7 purchase totals =	$693.88		$732.9592	$732.96	$732.95	$732.90