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	$217.45	5.148%	$228.6443	$228.64	$228.65	$228.60
Purchase #2	$80.48	6.284%	$85.5374	$85.54	$85.55	$85.50
Purchase #3	$73.87	10.245%	$81.438	$81.44	$81.45	$81.40
Purchase #4	$91.49	13.674%	$104.0003	$104.00	$104.00	$104.00
Purchase #5	$74.94	9.615%	$82.1455	$82.15	$82.15	$82.10
Purchase #6	$198.64	9.179%	$216.8732	$216.87	$216.85	$216.90
Purchase #7	$188.80	10.607%	$208.826	$208.83	$208.85	$208.80
7 purchase totals =	$925.67		$1,007.4647	$1,007.47	$1,007.50	$1,007.30