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	$193.38	8.531%	$209.8772	$209.88	$209.90	$209.90
Purchase #2	$114.53	5.331%	$120.6356	$120.64	$120.65	$120.60
Purchase #3	$138.36	10.255%	$152.5488	$152.55	$152.55	$152.50
Purchase #4	$213.83	7.644%	$230.1752	$230.18	$230.20	$230.20
Purchase #5	$173.96	13.126%	$196.794	$196.79	$196.80	$196.80
Purchase #6	$152.88	4.304%	$159.46	$159.46	$159.45	$159.50
Purchase #7	$72.91	5.662%	$77.0382	$77.04	$77.05	$77.00
7 purchase totals =	$1,059.85		$1,146.5290	$1,146.54	$1,146.60	$1,146.50