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	$14.72	3.473%	$15.2312	$15.23	$15.25	$15.20
Purchase #2	$176.93	10.136%	$194.8636	$194.86	$194.85	$194.90
Purchase #3	$233.75	5.615%	$246.8751	$246.88	$246.90	$246.90
Purchase #4	$147.83	5.224%	$155.5526	$155.55	$155.55	$155.60
Purchase #5	$73.45	6.826%	$78.4637	$78.46	$78.45	$78.50
Purchase #6	$165.97	7.447%	$178.3298	$178.33	$178.35	$178.30
Purchase #7	$133.90	4.593%	$140.05	$140.05	$140.05	$140.10
7 purchase totals =	$946.55		$1,009.3660	$1,009.36	$1,009.40	$1,009.50