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	$63.57	13.837%	$72.3662	$72.37	$72.35	$72.40
Purchase #2	$119.67	7.778%	$128.9779	$128.98	$129.00	$129.00
Purchase #3	$217.73	3.301%	$224.9173	$224.92	$224.90	$224.90
Purchase #4	$145.92	13.842%	$166.1182	$166.12	$166.10	$166.10
Purchase #5	$39.60	3.129%	$40.8391	$40.84	$40.85	$40.80
Purchase #6	$206.31	4.109%	$214.7873	$214.79	$214.80	$214.80
Purchase #7	$231.44	4.760%	$242.4565	$242.46	$242.45	$242.50
7 purchase totals =	$1,024.24		$1,090.4625	$1,090.48	$1,090.45	$1,090.50