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	$119.67	7.334%	$128.4466	$128.45	$128.45	$128.40
Purchase #2	$12.73	5.839%	$13.4733	$13.47	$13.45	$13.50
Purchase #3	$119.57	4.524%	$124.9793	$124.98	$125.00	$125.00
Purchase #4	$68.57	11.703%	$76.5947	$76.59	$76.60	$76.60
Purchase #5	$147.85	13.632%	$168.0049	$168.00	$168.00	$168.00
Purchase #6	$40.31	5.622%	$42.5762	$42.58	$42.60	$42.60
Purchase #7	$162.30	5.833%	$171.767	$171.77	$171.75	$171.80
7 purchase totals =	$671.00		$725.8420	$725.84	$725.85	$725.90