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	$200.29	9.598%	$219.5138	$219.51	$219.50	$219.50
Purchase #2	$20.73	5.442%	$21.8581	$21.86	$21.85	$21.90
Purchase #3	$120.92	12.765%	$136.3554	$136.36	$136.35	$136.40
Purchase #4	$189.94	5.677%	$200.7229	$200.72	$200.70	$200.70
Purchase #5	$222.62	4.145%	$231.8476	$231.85	$231.85	$231.80
Purchase #6	$138.46	4.222%	$144.3058	$144.31	$144.30	$144.30
Purchase #7	$210.41	7.698%	$226.6074	$226.61	$226.60	$226.60
7 purchase totals =	$1,103.37		$1,181.2110	$1,181.22	$1,181.15	$1,181.20