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	$183.59	3.210%	$189.4832	$189.48	$189.50	$189.50
Purchase #2	$222.84	8.289%	$241.3112	$241.31	$241.30	$241.30
Purchase #3	$229.59	8.335%	$248.7263	$248.73	$248.75	$248.70
Purchase #4	$117.60	13.820%	$133.8523	$133.85	$133.85	$133.90
Purchase #5	$110.90	4.110%	$115.458	$115.46	$115.45	$115.50
Purchase #6	$86.39	3.861%	$89.7255	$89.73	$89.75	$89.70
Purchase #7	$65.60	3.755%	$68.0633	$68.06	$68.05	$68.10
7 purchase totals =	$1,016.51		$1,086.6198	$1,086.62	$1,086.65	$1,086.70