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	$164.91	9.300%	$180.2466	$180.25	$180.25	$180.20
Purchase #2	$62.38	11.530%	$69.5724	$69.57	$69.55	$69.60
Purchase #3	$192.36	12.579%	$216.557	$216.56	$216.55	$216.60
Purchase #4	$224.63	4.734%	$235.264	$235.26	$235.25	$235.30
Purchase #5	$93.79	9.710%	$102.897	$102.90	$102.90	$102.90
Purchase #6	$199.83	11.551%	$222.9124	$222.91	$222.90	$222.90
Purchase #7	$40.84	4.148%	$42.534	$42.53	$42.55	$42.50
7 purchase totals =	$978.74		$1,069.9834	$1,069.98	$1,069.95	$1,070.00