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	$94.59	9.727%	$103.7908	$103.79	$103.80	$103.80
Purchase #2	$180.68	9.164%	$197.2375	$197.24	$197.25	$197.20
Purchase #3	$51.28	6.249%	$54.4845	$54.48	$54.50	$54.50
Purchase #4	$104.65	4.636%	$109.5016	$109.50	$109.50	$109.50
Purchase #5	$42.96	5.387%	$45.2743	$45.27	$45.25	$45.30
Purchase #6	$211.53	7.129%	$226.61	$226.61	$226.60	$226.60
Purchase #7	$112.46	5.688%	$118.8567	$118.86	$118.85	$118.90
7 purchase totals =	$798.15		$855.7554	$855.75	$855.75	$855.80