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	$181.62	13.698%	$206.4983	$206.50	$206.50	$206.50
Purchase #2	$174.79	11.124%	$194.2336	$194.23	$194.25	$194.20
Purchase #3	$92.83	11.260%	$103.2827	$103.28	$103.30	$103.30
Purchase #4	$215.94	4.270%	$225.1606	$225.16	$225.15	$225.20
Purchase #5	$86.32	8.311%	$93.4941	$93.49	$93.50	$93.50
Purchase #6	$94.57	5.588%	$99.8546	$99.85	$99.85	$99.90
Purchase #7	$240.61	6.760%	$256.8752	$256.88	$256.90	$256.90
7 purchase totals =	$1,086.68		$1,179.3991	$1,179.39	$1,179.45	$1,179.50