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	$141.67	7.402%	$152.1564	$152.16	$152.15	$152.20
Purchase #2	$19.48	8.703%	$21.1753	$21.18	$21.20	$21.20
Purchase #3	$127.47	13.578%	$144.7779	$144.78	$144.80	$144.80
Purchase #4	$165.61	12.124%	$185.6886	$185.69	$185.70	$185.70
Purchase #5	$206.76	4.195%	$215.4336	$215.43	$215.45	$215.40
Purchase #6	$213.72	11.513%	$238.3256	$238.33	$238.35	$238.30
Purchase #7	$116.52	5.800%	$123.2782	$123.28	$123.30	$123.30
7 purchase totals =	$991.23		$1,080.8356	$1,080.85	$1,080.95	$1,080.90