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	$181.32	5.765%	$191.7731	$191.77	$191.75	$191.80
Purchase #2	$52.53	8.831%	$57.1689	$57.17	$57.15	$57.20
Purchase #3	$171.29	5.587%	$180.86	$180.86	$180.85	$180.90
Purchase #4	$235.95	8.289%	$255.5079	$255.51	$255.50	$255.50
Purchase #5	$103.58	11.105%	$115.0826	$115.08	$115.10	$115.10
Purchase #6	$139.93	3.547%	$144.8933	$144.89	$144.90	$144.90
Purchase #7	$85.73	7.511%	$92.1692	$92.17	$92.15	$92.20
7 purchase totals =	$970.33		$1,037.4550	$1,037.45	$1,037.40	$1,037.60