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	$231.36	8.139%	$250.1904	$250.19	$250.20	$250.20
Purchase #2	$150.63	9.351%	$164.7154	$164.72	$164.70	$164.70
Purchase #3	$166.86	9.117%	$182.0726	$182.07	$182.05	$182.10
Purchase #4	$210.60	5.615%	$222.4252	$222.43	$222.45	$222.40
Purchase #5	$42.30	4.817%	$44.3376	$44.34	$44.35	$44.30
Purchase #6	$133.39	9.326%	$145.83	$145.83	$145.85	$145.80
Purchase #7	$233.59	9.619%	$256.059	$256.06	$256.05	$256.10
7 purchase totals =	$1,168.73		$1,265.6302	$1,265.64	$1,265.65	$1,265.60