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	$161.75	6.263%	$171.8804	$171.88	$171.90	$171.90
Purchase #2	$79.91	13.180%	$90.4421	$90.44	$90.45	$90.40
Purchase #3	$87.96	5.642%	$92.9227	$92.92	$92.90	$92.90
Purchase #4	$169.88	8.775%	$184.787	$184.79	$184.80	$184.80
Purchase #5	$93.88	12.259%	$105.3887	$105.39	$105.40	$105.40
Purchase #6	$139.86	12.683%	$157.5984	$157.60	$157.60	$157.60
Purchase #7	$164.78	8.255%	$178.3826	$178.38	$178.40	$178.40
7 purchase totals =	$898.02		$981.4019	$981.40	$981.45	$981.40