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	$9.72	13.118%	$10.9951	$11.00	$11.00	$11.00
Purchase #2	$9.86	4.467%	$10.3004	$10.30	$10.30	$10.30
Purchase #3	$196.81	6.561%	$209.7227	$209.72	$209.70	$209.70
Purchase #4	$147.84	11.520%	$164.8712	$164.87	$164.85	$164.90
Purchase #5	$10.65	7.604%	$11.4598	$11.46	$11.45	$11.50
Purchase #6	$38.33	12.218%	$43.0132	$43.01	$43.00	$43.00
Purchase #7	$123.84	11.844%	$138.5076	$138.51	$138.50	$138.50
7 purchase totals =	$537.05		$588.8700	$588.87	$588.80	$588.90