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	$158.34	3.577%	$164.0038	$164.00	$164.00	$164.00
Purchase #2	$140.44	10.557%	$155.2663	$155.27	$155.25	$155.30
Purchase #3	$176.75	7.498%	$190.0027	$190.00	$190.00	$190.00
Purchase #4	$120.69	6.219%	$128.1957	$128.20	$128.20	$128.20
Purchase #5	$130.38	9.363%	$142.5875	$142.59	$142.60	$142.60
Purchase #6	$152.58	10.537%	$168.6574	$168.66	$168.65	$168.70
Purchase #7	$174.51	6.457%	$185.7781	$185.78	$185.80	$185.80
7 purchase totals =	$1,053.69		$1,134.4915	$1,134.50	$1,134.50	$1,134.60