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	$33.61	6.610%	$35.8316	$35.83	$35.85	$35.80
Purchase #2	$83.70	4.540%	$87.5	$87.50	$87.50	$87.50
Purchase #3	$216.26	5.831%	$228.8701	$228.87	$228.85	$228.90
Purchase #4	$219.26	4.688%	$229.5389	$229.54	$229.55	$229.50
Purchase #5	$224.84	9.377%	$245.9232	$245.92	$245.90	$245.90
Purchase #6	$43.78	3.458%	$45.2939	$45.29	$45.30	$45.30
Purchase #7	$96.91	6.262%	$102.9785	$102.98	$103.00	$103.00
7 purchase totals =	$918.36		$975.9362	$975.93	$975.95	$975.90