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	$122.37	11.788%	$136.795	$136.80	$136.80	$136.80
Purchase #2	$73.26	9.495%	$80.216	$80.22	$80.20	$80.20
Purchase #3	$215.97	13.210%	$244.4996	$244.50	$244.50	$244.50
Purchase #4	$86.78	11.606%	$96.8517	$96.85	$96.85	$96.90
Purchase #5	$219.40	11.576%	$244.7977	$244.80	$244.80	$244.80
Purchase #6	$100.82	4.182%	$105.0363	$105.04	$105.05	$105.00
Purchase #7	$103.33	4.838%	$108.3291	$108.33	$108.35	$108.30
7 purchase totals =	$921.93		$1,016.5254	$1,016.54	$1,016.55	$1,016.50