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	$37.39	9.794%	$41.052	$41.05	$41.05	$41.10
Purchase #2	$198.69	10.648%	$219.8465	$219.85	$219.85	$219.80
Purchase #3	$242.96	5.136%	$255.4384	$255.44	$255.45	$255.40
Purchase #4	$54.30	8.156%	$58.7287	$58.73	$58.75	$58.70
Purchase #5	$168.54	7.185%	$180.6496	$180.65	$180.65	$180.60
Purchase #6	$217.59	7.561%	$234.042	$234.04	$234.05	$234.00
Purchase #7	$40.76	6.687%	$43.4856	$43.49	$43.50	$43.50
7 purchase totals =	$960.23		$1,033.2428	$1,033.25	$1,033.30	$1,033.10