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	$131.67	12.696%	$148.3868	$148.39	$148.40	$148.40
Purchase #2	$238.64	7.321%	$256.1108	$256.11	$256.10	$256.10
Purchase #3	$227.85	12.607%	$256.575	$256.58	$256.60	$256.60
Purchase #4	$170.95	9.704%	$187.539	$187.54	$187.55	$187.50
Purchase #5	$205.47	7.127%	$220.1138	$220.11	$220.10	$220.10
Purchase #6	$218.59	9.111%	$238.5057	$238.51	$238.50	$238.50
Purchase #7	$139.69	9.712%	$153.2567	$153.26	$153.25	$153.30
7 purchase totals =	$1,332.86		$1,460.4878	$1,460.50	$1,460.50	$1,460.50