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	$108.36	3.494%	$112.1461	$112.15	$112.15	$112.10
Purchase #2	$182.46	9.409%	$199.6277	$199.63	$199.65	$199.60
Purchase #3	$154.93	12.464%	$174.2405	$174.24	$174.25	$174.20
Purchase #4	$84.75	6.342%	$90.1248	$90.12	$90.10	$90.10
Purchase #5	$143.49	10.288%	$158.2523	$158.25	$158.25	$158.30
Purchase #6	$243.90	11.179%	$271.1656	$271.17	$271.15	$271.20
Purchase #7	$163.38	7.157%	$175.0731	$175.07	$175.05	$175.10
7 purchase totals =	$1,081.27		$1,180.6301	$1,180.63	$1,180.60	$1,180.60