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	$209.69	13.493%	$237.9835	$237.98	$238.00	$238.00
Purchase #2	$164.63	11.599%	$183.7254	$183.73	$183.75	$183.70
Purchase #3	$12.86	9.451%	$14.0754	$14.08	$14.10	$14.10
Purchase #4	$78.80	11.112%	$87.5563	$87.56	$87.55	$87.60
Purchase #5	$218.28	11.554%	$243.5001	$243.50	$243.50	$243.50
Purchase #6	$88.31	9.710%	$96.8849	$96.88	$96.90	$96.90
Purchase #7	$90.86	9.863%	$99.8215	$99.82	$99.80	$99.80
7 purchase totals =	$863.43		$963.5471	$963.55	$963.60	$963.60