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	$181.82	4.839%	$190.6183	$190.62	$190.60	$190.60
Purchase #2	$5.46	11.630%	$6.095	$6.10	$6.10	$6.10
Purchase #3	$74.57	10.659%	$82.5184	$82.52	$82.50	$82.50
Purchase #4	$197.46	12.577%	$222.2945	$222.29	$222.30	$222.30
Purchase #5	$18.74	8.309%	$20.2971	$20.30	$20.30	$20.30
Purchase #6	$198.43	13.467%	$225.1526	$225.15	$225.15	$225.20
Purchase #7	$213.94	5.525%	$225.7602	$225.76	$225.75	$225.80
7 purchase totals =	$890.42		$972.7361	$972.74	$972.70	$972.80