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	$181.59	3.431%	$187.8204	$187.82	$187.80	$187.80
Purchase #2	$164.50	12.468%	$185.0099	$185.01	$185.00	$185.00
Purchase #3	$55.96	12.255%	$62.8179	$62.82	$62.80	$62.80
Purchase #4	$240.35	7.431%	$258.2104	$258.21	$258.20	$258.20
Purchase #5	$114.42	9.560%	$125.3586	$125.36	$125.35	$125.40
Purchase #6	$224.70	6.173%	$238.5707	$238.57	$238.55	$238.60
Purchase #7	$17.50	7.745%	$18.8554	$18.86	$18.85	$18.90
7 purchase totals =	$999.02		$1,076.6433	$1,076.65	$1,076.55	$1,076.70