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	$176.48	7.396%	$189.5325	$189.53	$189.55	$189.50
Purchase #2	$83.93	7.585%	$90.2961	$90.30	$90.30	$90.30
Purchase #3	$32.72	11.430%	$36.4599	$36.46	$36.45	$36.50
Purchase #4	$110.47	6.475%	$117.6229	$117.62	$117.60	$117.60
Purchase #5	$138.62	11.373%	$154.3853	$154.39	$154.40	$154.40
Purchase #6	$85.72	11.492%	$95.5709	$95.57	$95.55	$95.60
Purchase #7	$233.83	7.619%	$251.6455	$251.65	$251.65	$251.60
7 purchase totals =	$861.77		$935.5131	$935.52	$935.50	$935.50