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	$43.54	5.339%	$45.8646	$45.86	$45.85	$45.90
Purchase #2	$39.53	12.338%	$44.4072	$44.41	$44.40	$44.40
Purchase #3	$202.32	8.608%	$219.7357	$219.74	$219.75	$219.70
Purchase #4	$51.82	7.173%	$55.537	$55.54	$55.55	$55.50
Purchase #5	$91.74	9.826%	$100.7544	$100.75	$100.75	$100.80
Purchase #6	$112.98	5.863%	$119.604	$119.60	$119.60	$119.60
Purchase #7	$183.98	13.380%	$208.5965	$208.60	$208.60	$208.60
7 purchase totals =	$725.91		$794.4994	$794.50	$794.50	$794.50