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	$139.45	8.774%	$151.6853	$151.69	$151.70	$151.70
Purchase #2	$152.74	7.670%	$164.4552	$164.46	$164.45	$164.50
Purchase #3	$37.78	9.243%	$41.272	$41.27	$41.25	$41.30
Purchase #4	$183.39	4.833%	$192.2532	$192.25	$192.25	$192.30
Purchase #5	$166.29	12.172%	$186.5308	$186.53	$186.55	$186.50
Purchase #6	$18.56	4.730%	$19.4379	$19.44	$19.45	$19.40
Purchase #7	$246.94	10.774%	$273.5453	$273.55	$273.55	$273.50
7 purchase totals =	$945.15		$1,029.1797	$1,029.19	$1,029.20	$1,029.20