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	$40.71	6.451%	$43.3362	$43.34	$43.35	$43.30
Purchase #2	$168.79	13.579%	$191.71	$191.71	$191.70	$191.70
Purchase #3	$206.83	4.541%	$216.2222	$216.22	$216.20	$216.20
Purchase #4	$142.56	9.371%	$155.9193	$155.92	$155.90	$155.90
Purchase #5	$73.40	12.485%	$82.564	$82.56	$82.55	$82.60
Purchase #6	$92.70	9.590%	$101.5899	$101.59	$101.60	$101.60
Purchase #7	$222.84	4.326%	$232.4801	$232.48	$232.50	$232.50
7 purchase totals =	$947.83		$1,023.8217	$1,023.82	$1,023.80	$1,023.80