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	$162.94	10.752%	$180.4593	$180.46	$180.45	$180.50
Purchase #2	$90.87	5.385%	$95.7633	$95.76	$95.75	$95.80
Purchase #3	$203.60	13.154%	$230.3815	$230.38	$230.40	$230.40
Purchase #4	$63.60	5.221%	$66.9206	$66.92	$66.90	$66.90
Purchase #5	$209.66	6.360%	$222.9944	$222.99	$223.00	$223.00
Purchase #6	$188.76	6.228%	$200.516	$200.52	$200.50	$200.50
Purchase #7	$105.68	3.466%	$109.3429	$109.34	$109.35	$109.30
7 purchase totals =	$1,025.11		$1,106.3780	$1,106.37	$1,106.35	$1,106.40