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	$194.66	8.484%	$211.175	$211.18	$211.20	$211.20
Purchase #2	$242.80	7.269%	$260.4491	$260.45	$260.45	$260.40
Purchase #3	$137.96	9.580%	$151.1766	$151.18	$151.20	$151.20
Purchase #4	$143.26	6.537%	$152.6249	$152.62	$152.60	$152.60
Purchase #5	$238.58	7.108%	$255.5383	$255.54	$255.55	$255.50
Purchase #6	$108.57	9.353%	$118.7246	$118.72	$118.70	$118.70
Purchase #7	$90.84	10.402%	$100.2892	$100.29	$100.30	$100.30
7 purchase totals =	$1,156.67		$1,249.9777	$1,249.98	$1,250.00	$1,249.90