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	$150.42	8.159%	$162.6928	$162.69	$162.70	$162.70
Purchase #2	$113.77	8.487%	$123.4257	$123.43	$123.45	$123.40
Purchase #3	$153.73	8.767%	$167.2075	$167.21	$167.20	$167.20
Purchase #4	$23.78	7.339%	$25.5252	$25.53	$25.55	$25.50
Purchase #5	$210.37	10.540%	$232.543	$232.54	$232.55	$232.50
Purchase #6	$126.62	9.818%	$139.0516	$139.05	$139.05	$139.10
Purchase #7	$154.47	9.301%	$168.8373	$168.84	$168.85	$168.80
7 purchase totals =	$933.16		$1,019.2831	$1,019.29	$1,019.35	$1,019.20