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	$136.63	13.439%	$154.9917	$154.99	$155.00	$155.00
Purchase #2	$159.30	3.402%	$164.7194	$164.72	$164.70	$164.70
Purchase #3	$213.28	9.563%	$233.676	$233.68	$233.70	$233.70
Purchase #4	$162.94	11.653%	$181.9274	$181.93	$181.95	$181.90
Purchase #5	$43.85	3.386%	$45.3348	$45.33	$45.35	$45.30
Purchase #6	$132.48	7.846%	$142.8744	$142.87	$142.85	$142.90
Purchase #7	$35.30	6.853%	$37.7191	$37.72	$37.70	$37.70
7 purchase totals =	$883.78		$961.2428	$961.24	$961.25	$961.20