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	$240.83	10.676%	$266.541	$266.54	$266.55	$266.50
Purchase #2	$91.47	10.145%	$100.7496	$100.75	$100.75	$100.70
Purchase #3	$181.30	13.374%	$205.5471	$205.55	$205.55	$205.50
Purchase #4	$10.39	3.277%	$10.7305	$10.73	$10.75	$10.70
Purchase #5	$213.65	5.313%	$225.0012	$225.00	$225.00	$225.00
Purchase #6	$54.91	9.138%	$59.9277	$59.93	$59.95	$59.90
Purchase #7	$217.25	11.544%	$242.3293	$242.33	$242.35	$242.30
7 purchase totals =	$1,009.80		$1,110.8264	$1,110.83	$1,110.90	$1,110.60