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	$140.81	10.669%	$155.833	$155.83	$155.85	$155.80
Purchase #2	$234.29	8.127%	$253.3307	$253.33	$253.35	$253.30
Purchase #3	$180.25	9.161%	$196.7627	$196.76	$196.75	$196.80
Purchase #4	$165.60	9.798%	$181.8255	$181.83	$181.85	$181.80
Purchase #5	$218.29	11.510%	$243.4152	$243.42	$243.40	$243.40
Purchase #6	$114.44	12.553%	$128.8057	$128.81	$128.80	$128.80
Purchase #7	$206.91	4.393%	$215.9996	$216.00	$216.00	$216.00
7 purchase totals =	$1,260.59		$1,375.9724	$1,375.98	$1,376.00	$1,375.90