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	$159.79	4.562%	$167.0796	$167.08	$167.10	$167.10
Purchase #2	$204.42	8.224%	$221.2315	$221.23	$221.25	$221.20
Purchase #3	$201.66	10.553%	$222.9412	$222.94	$222.95	$222.90
Purchase #4	$178.72	3.705%	$185.3416	$185.34	$185.35	$185.30
Purchase #5	$63.71	10.268%	$70.2517	$70.25	$70.25	$70.30
Purchase #6	$29.93	9.513%	$32.7772	$32.78	$32.80	$32.80
Purchase #7	$176.33	6.442%	$187.6892	$187.69	$187.70	$187.70
7 purchase totals =	$1,014.56		$1,087.3120	$1,087.31	$1,087.40	$1,087.30