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	$139.33	10.464%	$153.9095	$153.91	$153.90	$153.90
Purchase #2	$119.89	3.232%	$123.7648	$123.76	$123.75	$123.80
Purchase #3	$32.86	8.677%	$35.7113	$35.71	$35.70	$35.70
Purchase #4	$178.64	12.173%	$200.3858	$200.39	$200.40	$200.40
Purchase #5	$191.36	4.502%	$199.975	$199.98	$200.00	$200.00
Purchase #6	$162.25	3.848%	$168.4934	$168.49	$168.50	$168.50
Purchase #7	$151.60	9.865%	$166.5553	$166.56	$166.55	$166.60
7 purchase totals =	$975.93		$1,048.7951	$1,048.80	$1,048.80	$1,048.90