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	$53.50	10.850%	$59.3048	$59.30	$59.30	$59.30
Purchase #2	$96.48	4.865%	$101.1738	$101.17	$101.15	$101.20
Purchase #3	$172.87	3.646%	$179.1728	$179.17	$179.15	$179.20
Purchase #4	$192.42	13.180%	$217.781	$217.78	$217.80	$217.80
Purchase #5	$183.60	9.412%	$200.8804	$200.88	$200.90	$200.90
Purchase #6	$119.27	9.601%	$130.7211	$130.72	$130.70	$130.70
Purchase #7	$212.94	6.732%	$227.2751	$227.28	$227.30	$227.30
7 purchase totals =	$1,031.08		$1,116.3090	$1,116.30	$1,116.30	$1,116.40